Under kitchen-sink disposal erratic plumbing

[PJB12]

Does plumbing code stipulate a rigid pipe for the vent or could it be something flexible and easier to drop down from above than a rigid pipe?

Even though flexible PVC exists up to 4" diameter; as of my last code update class, perhaps 6 years ago, flexible was still not allowed for DWV.

The reasoning is that a dip could appear. The dip will eventually fill with water- be it either condensate or rain that rolled in from the VTR to which it's connected. The trapped water will prevent air from being drawn in while the fixture below drains, thus the P-trap will be vacuumed dry.

I believe that Schedule 30 PVC is the thinnest wall that is allowed and it is not allowed in some places.

If overhead clearance doesn't exist to drop in a long length, shorter pieces with couplings attached may workout for you. When you tie to the vent through the roof, be sure to tie in below where the size increases under the roof. (If you live in an always warm climate, it may not increase.)



Out The Wall & Up?:
That opens a pandora's box of rules.

If you go out the wall & up, under IPC & UPC the vent will have to end above the eave if the eave has vents. It'll have to to end >10 feet from average finished grade. And there are a bunch of rules about clearance to windows, doors & stuff. Search "IPC chapter nine" on line for the mess. Section 903 has (too) many pertinent details.

Very Important is 903.7 (if I remember correctly. It's maybe 903.9). Your climate may prohibit the vent going up an outside wall unless it is protected against freezing. To verify your climate's requirements, search for the formula using the term "97.5% Value". If the value calculates to zero-F, you have to protect against freezing.

Around here, outside vents are rare on houses. Usually people build a chase inside the house instead. I've seen commercial & industrial locations where the outdoor vent pipe is wrapped with heat tape and the chase has insulation. But, it's always cast iron pipe due to the heat tape vs fire hazard.

Sorry for taking away your easy flex pipe way.
Paul

 

[Ron Van]

Interestingly, a toilet trap is an S-Trap.

This is true! A toilet is the only S Trap allowed though.

They are designed so the water leaving is slow enough & there is enough wash-down volume that is timed not to let the trap be drawn dry.

A toilet uses the physics concerning a siphon to do it's job but then refills slowly to refill the trap without a siphon reforming. This is not the case with all other traps though.

I suppose the bottom line is: "Your House, Your Rules".
No problems in all of these years indicates a safely functioning drain. In a daily use room like a kitchen, you'll know quickly if the trap ever loses its seal.

At worst, when you sell the buyer's home inspector might be bright enough to catch it,

Yes, Home inspectors are pretty hit and miss on code violations. They are more likely to notice a missing smoke detector than a wiring problem in the attic.

but I doubt it very much. Yours is not obviously outside of the rather obscure code reference.

I was surprised to learn that in the IPC Plumbing code, there is a chapter devoted specifically to vents. Chapter 9 has 19 sections of vent rules whereas Chapter 5 (Water Heaters) only has 5 sections. It seems that there is more code devoted specifically to vents than water heaters or just about anything else. If a home inspector was good, a vent problem would be noticeable and not too obscure however, my current house, which I bought in 2020, has 3 bathrooms and 2 kitchens with S Traps that the inspector overlooked.

In the last house I sold, there was never any mention of codes or building permits or anything like that during the sale. Of course this was in the very lenient state of California . . . .(kidding about the lenient part). But once I had a water heater professionally installed in that house and the the plumber pulled a permit for that. The inspector that came out noticed that I had converted the garage into a music recording studio. He pointed to the wall I built on the inside of the roll up door. I said the wall was really a partition and it could be removed easily. The inspector said, "Okay" and left.

No loss of sleep necessary!

I lose sleep over stuff like this all the time. I would see a therapist but my daughter is a therapist and she cried for 3 days after the election....I think I'll skip the therapist.

My point is this....plumbing vents are easily misunderstood. They have several purposes but the #1 purpose is usually overlooked, and that is to prevent a siphon from forming and sucking the water out of the trap it serves. All traps (with the exception of the toilet) need a vent to prevent a siphon and all traps, (including a toilet) needs a vent to aid in the flow of drainage.

AAV's are allowed by IPC code and by approval in UPC code areas. There is quite a controversy about AAV's. Here's what Plumbing and Mechanical Engineers magazine says about it.

Proponents of air admittance valves want them added to the UPC code, but they face resistance from those who remain unconvinced.

A recent survey among readers of PM Engineer magazine revealed that 74 percent would consider the use of AAVs for venting systems, while 52 percent said they would use AAVs anywhere the code would allow. Currently, AAVs that comply to American Society of Sanitary Engineering (ASSE) 1050, 1051 and NSF Standard 14 are approved in the International Plumbing codes (IPC/IRC). But the Uniform Plumbing Code (UPC) only allows them under Section 301.2, Alternate Materials and Methods

Since an ANSI standard for AAV usage already exists, the UPC stands in conflict with other ANSI standards as long as AAVs are prohibited. This is one argument AAV proponents are using in their call for AAVs to be admitted fully into the UPC.

With respect to you for thinking of an auto vent, I think I'd be inclined to skip it.

Auto Vents are not approved by any code. The ones with a spring in them are not approved for houses, they are used in RV's because, I think, the movement of an RV down a road could cause a gravity type valve to open and close. A spring keeps it shut during road movement but this type is not allowed in a house.

An atmospheric (Traditional Vent) is ideal but according to Studor, an AAV may be better than an open air vent system. This is because (according to Studor) having an AAV close to the trap allows the AAV to sense negative pressure faster than an open air vent that is farther away. here's what Studor says;

The company's Air Admittance Valves (available in several models and capacities) open when the drain system senses negative pressure as low as 0.1 psi, but will remain closed at 0 psi or above.

This vent is designed to open when the plumbing fixture(s) it serves are draining, thus allowing air to enter the drain waste vent system.

The Studor vent AAV closes (by gravity alone, no springs), when there is no wastewater flowing through the system, thus preventing sewer gas from passing up the drain or vent into the building.

According to Studor "This style air admittance valve is not recognized as a mechanical vent in the International Plumbing Coder (IPC)." - op. cit.

Excerpting from the Studor manual:

Because AAVs are either at or very near the Point Of Need (PON) for air, and thanks to their reaction times, a system utilizing STUDOR AAVs is capable of balancing its internal pressure much more efficiently, without trap movement or depletion than open pipe vent systems.

This is particularly true in large commercial applications where the air needed to balance the system after each occurrence is drawn from far away points and thus require substantial time to reach the Point Of Need (PON). - op. cit.

There are some really good reasons to use an AAV.
A friend of mine who built a house in Alaska said he wanted as few roof penetrations as possible (because of harsh weather) so he has the one atmospheric vent that is required to handle positive pressures and all the rest are AAV. They can be in the attic (if possible) to exclude the possibility of flooding like you mentioned.

But in a kitchen island (for example) putting the AAV above the flood plane may not be possible...but it's Okay. They are approved for installation below the flood plane.

Two problems with adding a mechanical vent quickly come to mind-
A) If the drain past the vent clogs or even slows, particles from the disposer waste can lodge under the diaphragm and allow sewer gas to escape into the room.

This shouldn't happen though, if the vent is operating normally, because the vent closes with positive pressure. No debris should get to the diaphragm. If waste water spews out of the AAV vent, it should be taken off by unscrewing it and inspected or replaced.

B) In many jurisdictions (like here), the diaphragm of the vent has to be above the flood rim of the vessel.

The approved AAV's these days only have to be 4" above the trap.

IPC 917.4 Location. Individual and branch-type air admittance
valves shall be located a minimum of 4 inches (102 mm) above
the horizontal branch drain or fixture drain being vented.


Here's one I installed in my own home.

The plumbing is confined to the rear of the cabinet allowing storage in the front. The little white thing under the disposal is a moisture sensor. The finished version of this installation includes a rubberized tray in the bottom of this cabinet to contain any water that "WILL" leak in here at some point in the future.



So, in summary, AAV's are allowed by most code. "S" Trap's are not allowed by any code and are dangerous. I would (and have) used an AAV to fix a vent problem. They are easy and work well.

 

[tk3000]

How about an air admittance valve/vent installed in a T after the trap? Doesn't part of the issue relate to where the vertical pipe below the floor joins a vented drain pipe?

I see studs on the back wall and suspect one could even get the air admittance valve high up in relation to the level of the sink.

Paul, thanks for info and insights. I had some faint memory regarding the “wier”, you made it clear to me. I have to double check the clerance from the wier when I return to Lansing, MI – hopefully at the beginning of next week.

I read that S-Traps have been banned in the US since 2006. But within the US other jurisdictions it was outlawed much earlier (1950s). Also, I was told that the builder who built that complex did not have a good reputation.

Also, I will do the test of pouring a small bucket of water into the sink to see if the siphon effect would be strong enough to the point whereas it depletes water from the s-trap.

“My parents once bought a home that was built in 1969 with 3 S-traps. They're even on the engineering prints. Beats me how the plumber got the variances. Before I changed it to a P-trap with proper venting, the kitchen one would go dry every time a full bowl of water was released or the disposer ran. Every time. “
=> Yeah, that is interesting. It also fills itself right after a flush replenishing that large vol. of water right away (an easy work around for a s-trap that is suffering from the siphon effect would be to simply add a little bit of extra after large usage). Having multiple toilet next to each of other would require a more robust venting (so, I read).

Yeah, I was already considering that solution you proposed! The stub of pvc coming from the floor could use a sanitary T coupled with a small piece of pvc and an intake air admittance valve atop of it. The following seem to be the relevant code for this case:


“IPC 918.4 Location.
Individual and branch-type air admittance valves shall be located a minimum of 4 inches (102 mm) above the horizontal branch drain or fixture drain being vented. Stack-type air admittance valves shall be located not less than 6 inches (152 mm) above the flood level rim of the highest fixture being vented. The air admittance valve shall be located within the maximum developed length permitted for the vent. The air admittance valve shall be installed not less than 6 inches (152 mm) above insulation materials.

“
I did not look or investigate close enough to know whether or not the combination of: sanitary T + AAV + small piece of PVC would be a good fit to this situation. In any case, that how the condo was built (I believe the other units are the same way). And, as you pointed out, I doubt the inspector would even notice it (in my experiences those home inspectors have a very generic, lacking and superficial understanding about things)

Also, I will take pic s at different angles to make it clear. In the end, I will probably improve on the slip joint plumbing contraption up close to the sink bowels (remove the T and increase the distance/sweep between the disposal and the vertical stack), and call it a day.

 

[tk3000]

I suppose the bottom line is: "Your House, Your Rules".
No problems in all of these years indicates a safely functioning drain. In a daily use room like a kitchen, you'll know quickly if the trap ever loses its seal.

At worst, when you sell the buyer's home inspector might be bright enough to catch it, but I doubt it very much. Yours is not obviously outside of the rather obscure code reference.

No loss of sleep necessary!

I only used a home inspector once – mainly because I was buying a house in another State. It is always good to have another pair of eyes looking into things though (you may miss something for lack or attention or not know about some particular thing, etc; but typically those things tend to be minor thing). Most of the test the inspector did perform, my mother could have performed without any issues.


For instance, parts of the unfinished basement did not have conduits going to the light switches. Since it was something that would be relatively easy to address, I did not complain or anything; but, yeah, for most part a home inspector is a waste of money.

 

[tk3000]

This is true! A toilet is the only S Trap allowed though.

A toilet uses the physics concerning a siphon to do it's job but then refills slowly to refill the trap without a siphon reforming. This is not the case with all other traps though.

Yes, Home inspectors are pretty hit and miss on code violations. They are more likely to notice a missing smoke detector than a wiring problem in the attic.

I was surprised to learn that in the IPC Plumbing code, there is a chapter devoted specifically to vents. Chapter 9 has 19 sections of vent rules whereas Chapter 5 (Water Heaters) only has 5 sections. It seems that there is more code devoted specifically to vents than water heaters or just about anything else. If a home inspector was good, a vent problem would be noticeable and not too obscure however, my current house, which I bought in 2020, has 3 bathrooms and 2 kitchens with S Traps that the inspector overlooked.

In the last house I sold, there was never any mention of codes or building permits or anything like that during the sale. Of course this was in the very lenient state of California . . . .(kidding about the lenient part). But once I had a water heater professionally installed in that house and the the plumber pulled a permit for that. The inspector that came out noticed that I had converted the garage into a music recording studio. He pointed to the wall I built on the inside of the roll up door. I said the wall was really a partition and it could be removed easily. The inspector said, "Okay" and left.

I lose sleep over stuff like this all the time. I would see a therapist but my daughter is a therapist and she cried for 3 days after the election....I think I'll skip the therapist.

My point is this....plumbing vents are easily misunderstood. They have several purposes but the #1 purpose is usually overlooked, and that is to prevent a siphon from forming and sucking the water out of the trap it serves. All traps (with the exception of the toilet) need a vent to prevent a siphon and all traps, (including a toilet) needs a vent to aid in the flow of drainage.

AAV's are allowed by IPC code and by approval in UPC code areas. There is quite a controversy about AAV's. Here's what Plumbing and Mechanical Engineers magazine says about it.

Proponents of air admittance valves want them added to the UPC code, but they face resistance from those who remain unconvinced.

A recent survey among readers of PM Engineer magazine revealed that 74 percent would consider the use of AAVs for venting systems, while 52 percent said they would use AAVs anywhere the code would allow. Currently, AAVs that comply to American Society of Sanitary Engineering (ASSE) 1050, 1051 and NSF Standard 14 are approved in the International Plumbing codes (IPC/IRC). But the Uniform Plumbing Code (UPC) only allows them under Section 301.2, Alternate Materials and Methods

Since an ANSI standard for AAV usage already exists, the UPC stands in conflict with other ANSI standards as long as AAVs are prohibited. This is one argument AAV proponents are using in their call for AAVs to be admitted fully into the UPC.


Auto Vents are not approved by any code. The ones with a spring in them are not approved for houses, they are used in RV's because, I think, the movement of an RV down a road could cause a gravity type valve to open and close. A spring keeps it shut during road movement but this type is not allowed in a house.

An atmospheric (Traditional Vent) is ideal but according to Studor, an AAV may be better than an open air vent system. This is because (according to Studor) having an AAV close to the trap allows the AAV to sense negative pressure faster than an open air vent that is farther away. here's what Studor says;

The company's Air Admittance Valves (available in several models and capacities) open when the drain system senses negative pressure as low as 0.1 psi, but will remain closed at 0 psi or above.

This vent is designed to open when the plumbing fixture(s) it serves are draining, thus allowing air to enter the drain waste vent system.

The Studor vent AAV closes (by gravity alone, no springs), when there is no wastewater flowing through the system, thus preventing sewer gas from passing up the drain or vent into the building.

According to Studor "This style air admittance valve is not recognized as a mechanical vent in the International Plumbing Coder (IPC)." - op. cit.

Excerpting from the Studor manual:

Because AAVs are either at or very near the Point Of Need (PON) for air, and thanks to their reaction times, a system utilizing STUDOR AAVs is capable of balancing its internal pressure much more efficiently, without trap movement or depletion than open pipe vent systems.

This is particularly true in large commercial applications where the air needed to balance the system after each occurrence is drawn from far away points and thus require substantial time to reach the Point Of Need (PON). - op. cit.

There are some really good reasons to use an AAV.
A friend of mine who built a house in Alaska said he wanted as few roof penetrations as possible (because of harsh weather) so he has the one atmospheric vent that is required to handle positive pressures and all the rest are AAV. They can be in the attic (if possible) to exclude the possibility of flooding like you mentioned.

But in a kitchen island (for example) putting the AAV above the flood plane may not be possible...but it's Okay. They are approved for installation below the flood plane.



This shouldn't happen though, if the vent is operating normally, because the vent closes with positive pressure. No debris should get to the diaphragm. If waste water spews out of the AAV vent, it should be taken off by unscrewing it and inspected or replaced.

The approved AAV's these days only have to be 4" above the trap.

IPC 917.4 Location. Individual and branch-type air admittance
valves shall be located a minimum of 4 inches (102 mm) above
the horizontal branch drain or fixture drain being vented.


Here's one I installed in my own home.
View attachment 33744
The plumbing is confined to the rear of the cabinet allowing storage in the front. The little white thing under the disposal is a moisture sensor. The finished version of this installation includes a rubberized tray in the bottom of this cabinet to contain any water that "WILL" leak in here at some point in the future.

View attachment 33745

So, in summary, AAV's are allowed by most code. "S" Trap's are not allowed by any code and are dangerous. I would (and have) used an AAV to fix a vent problem. They are easy and work well.

Thanks! You got all the main points covered. Usually, I type posts in a text editor and then post it afterwards; so, I missed your post before the final draft. I should have refreshed my browser before posting it.

 

[PJB12]

This is true! A toilet is the only S Trap allowed though.



I was surprised to learn that in the IPC Plumbing code, there is a chapter devoted specifically to vents. Chapter 9 has 19 sections of vent rules whereas Chapter 5 (Water Heaters) only has 5 sections. It seems that there is more code devoted specifically to vents than water heaters or just about anything else. If a home inspector was good, a vent problem would be noticeable and not too obscure however, my current house, which I bought in 2020, has 3 bathrooms and 2 kitchens with S Traps that the inspector overlooked.

Interestingly, a university laboratory job I was on long ago was built with several S-Traps on purpose. The piping was 100% clear glass from roof penetration to a dilution station 6 floors down.

I can't remember the reason for the s-traps, but it was mandated on the prints. That's the only other place I've seen them. And only once.

We also forget that venting allows drainage from upstream fixtures to have a place to push the displaced air that is in front of the water. Vents do work ahead of and behind the water slug.

For AAVs, here we absolutely have to have the diaphragm above the flood rim. Local code is allowed to over-rule, I guess.

Regarding venting rules, your comment reminded me a of fond memory:
I was sitting in the patrol car at work waiting for crime scene or coroner or something, studying away for my journeyman's test with my handy flashlight. Oh boy! Vertical fixture group venting is easy! I've got this! So intuitive!

I moved to the horizontal fixture group venting section just in time for my partner to return to the car. She heard me muttering away and said "Horizontal group venting?". (She was a master plumber.)
Those rules didn't make any sense to me and still don't!


What's the name of the moisture sensor you have in the photo, Ron? I like how compact it is.

Paul

 

[PJB12]

I only used a home inspector once – mainly because I was buying a house in another State. It is always good to have another pair of eyes looking into things though (you may miss something for lack or attention or not know about some particular thing, etc; but typically those things tend to be minor thing). Most of the test the inspector did perform, my mother could have performed without any issues.


For instance, parts of the unfinished basement did not have conduits going to the light switches. Since it was something that would be relatively easy to address, I did not complain or anything; but, yeah, for most part a home inspector is a waste of money.

One suggestion about hiring an inspector, don't get one through your real estate agent, nor from the buyer's. There is a whole lot of incentive for a "fantastic!" inspection report. (Or so I was told by a real estate agent who saw the light and went honest.

One who sub contracts licensed people in each of the pertinent trades is ideal.

People forget to have videos all piping under ground and between floors. Save a copy of the video. Be sure to do all inside the perimeter and the building drain and sewer. Do the storm, too if it's accessible.

Paul

 

[Ron Van]

We also forget that venting allows drainage from upstream fixtures to have a place to push the displaced air that is in front of the water. Vents do work ahead of and behind the water slug.

I guess that's the reason for at least one mandated open air vent. Because that positive blast of air is in front of the water slug, it doesn't affect the water in the trap (if vented properly) but the positive air pressure still needs somewhere to go. I think it is most common for the main stack to extend all the way up and out the roof for the one mandatory open air vent. That's how it is at my house anyway.

For AAVs, here we absolutely have to have the diaphragm above the flood rim. Local code is allowed to over-rule, I guess.

Code adoption and approvals are slow and behind the technology. Europe had approved PEX decades before it was approved in the USA. Now PEX rules in the USA. I can't wait to see what's next...I guess we should look at what Europe is doing.

What's the name of the moisture sensor you have in the photo, Ron? I like how compact it is.

I got them off Amazon. I probably should check and/or replace them. They are loud enough to be heard easily. You can test them and then dry them off to reset.



I follow code most of the time. Usually always but I don't normally invite the government into my house to verify and see what I'm up to just like they don't tell me what they're up to.

Like you, I worked for a law enforcement agency (state) for over 30 years and I never had a problem with somebody who was following the law. When it comes to your house, though, you're expected to prove with inspections that you are not a chronic law breaker? Sounds like an authoritarian Nazi state.

Anyway, if I were @tk3000 , I would put an AAV on there in a heartbeat. We never determined if @tk3000 was in a UPC or IPC code area but either way, I'd do it. Unless he is doing a kitchen remodel, tearing out the wall and installing an atmospheric vent is out of the question. Leaving the S Trap would keep me up at night.

I already mentioned several good reasons to use an AAV. Here are a couple more...

When we bought our current house in 2020, I noticed that our house (built in 1970) and many others in the area had drains going straight down through the floor (just like @tk3000). Many had no vent, others had a vent. I asked someone why the drains didn’t go through the wall like I was used to seeing. The answer was because of freezing temps... and it’s easier to go straight down than through the wall. It doesn’t freeze here very often but when it does, it always catches people unprepared. If you live in Montana, you probably have it figured out better than we do down here in the South. Going straight down through the floor presents a small problem for venting. It can be done though. It’s a great reason for an AAV.

The other thing for me was, when I remodeled our kitchen, I discovered there was an original kitchen drain made out of galvanized pipe than had a traditional trap arm going into the wall. The galvanized trap arm was completely corroded through. Someone (previous to us) had bypassed it with PVC and ran the drain down through the floor via a S Trap. But because there is a window above the kitchen sink, the original galvanized trap arm had to cut through numerous studs and even the king stud and jack stud surrounding the window to get to a place where a vertical vent could be located. I know this is common and just the way it was done for many decades since indoor plumbing became a thing. I don't like it though. Cutting through all those studs doesn't make much sense to me. It's a case of plumber verses framer because I doubt the framers like it much either. So, going straight down through the floor with the drain makes sense for three reasons. 1) freeze protection 2) Ease of install and maintenance 3) less framing destruction. Going straight down with the drain presents a problem for venting though. An AAV solves this problem.

 

[PJB12]

I follow code most of the time. Usually always but I don't normally invite the government into my house to verify and see what I'm up to just like they don't tell me what they're up to.

At my house, I'll call for inspection if it's something that could cause an insurance company rejection of a claim, such as electrical or gas. Truthfully, I used to call for inspection to have a second set of "expert" eyes on the project. But, the "expert" part went out the window long ago. Believe it or not, where I live the electrical inspectors do not have to be electricians.

When we bought our current house in 2020, I noticed that our house (built in 1970) and many others in the area had drains going straight down through the floor (just like @tk3000). Many had no vent, others had a vent. I asked someone why the drains didn’t go through the wall like I was used to seeing. The answer was because of freezing temps... and it’s easier to go straight down than through the wall. It doesn’t freeze here very often but when it does, it always catches people unprepared. If you live in Montana, you probably have it figured out better than we do down here in the South.

Here in southeast Michigan we get freezing temps from late October to about mid march. The part of my house with the kitchen was built in about 1900. It has little wall insulation and certainly no wind break under the siding. Plumbing was added to the house in the 20's.

The galvanized sink drain used to go into the wall and down. That part of the kitchen is on a 24" cantilevered section that is hanging outside in mid air. Hoarfrost would close it often. Very often! I re-piped to have the required horizontal trap arm distance, then down. The horizontal under the floor still is in the overhang, but hasn't closed (yet...). I suppose being PVC instead of galvanized helps a bit.

The then existing galvanized water lines used to go into the wall and down. They'd freeze daily, probably because they were in the cantilevered section.

My solution was to bring the water lines up from the basement as close to the front of the cabinet as possible (still barely in the overhang). I ran them as close to the floor of the cabinet that coper 90's would allow, then to the back of the cabinet and up to angle stops.

But, what does one do with two copper pipes on the floor of the cabinet? I put drawer runner slides on the sides of the cabinet all the way to the bottom. I made a short sided drawer the size of the cabinet floor. It sure is convenient to pull the drawer out to get to stuff. The downside it that I'll have to take apart my masterpiece to remove the cabinet and I lost about 1" of height in the cabinet.

The west wall of the house had two copper tubing runs up the wall to the second floor for heat. They would also freeze just about every day. I re-ran that zone up an inside wall. The abandoned copper tubing now are chases for telephone, ethernet and antenna wires.

Weird size, too. The OD of the tubing is 1.295" and the walls are far heavier than Type L. The fittings are interesting, too. They are hand-hammered flare to NPT like those we used on lead water lines. It must be from very early in the copper days.

But because there is a window above the kitchen sink, the original galvanized trap arm had to cut through numerous studs and even the king stud and jack stud surrounding the window to get to a place where a vertical vent could be located.

The age-old argument on job sites! I guess the plumber won that one.

Plumbers always win. I wired a new construction mansion as a "pressured into it job" for a big shot at work. (I don't do residential except for friends or forced labor. Worse was that this was clock hours. Not my contractor rate.)
The building was specified all EMT conduit above grade. Walls (exterior and partition) were foam block with concrete fill and the floors on all 3 levels were poured. My rough-in had the green tag & was ready for devices and the elevator guys. Then things went backwards. Really backwards.

The plumber ran a 4" stack exactly on-center in front of the load center, 2" in front of the door. I couldn't open it to access a breaker, let alone get the job to pass. I was there long before plumbing rough-in, not even his underground was roughed. A couple of high 22-/12's would have shifted the stack plenty far away in this 14 foot tall basement.

In the end, he won. I moved the load center, reworked and rewired the service entrance and re-worked all of the conduits I'd already installed- plus spent a day on the rough re-inspect.
I was so happy to get out and go back to my nice, quiet and peaceful industrial work!

 

[tk3000]

I guess that's the reason for at least one mandated open air vent. Because that positive blast of air is in front of the water slug, it doesn't affect the water in the trap (if vented properly) but the positive air pressure still needs somewhere to go. I think it is most common for the main stack to extend all the way up and out the roof for the one mandatory open air vent. That's how it is at my house anyway.

Code adoption and approvals are slow and behind the technology. Europe had approved PEX decades before it was approved in the USA. Now PEX rules in the USA. I can't wait to see what's next...I guess we should look at what Europe is doing.

I got them off Amazon. I probably should check and/or replace them. They are loud enough to be heard easily. You can test them and then dry them off to reset.

View attachment 33760

I follow code most of the time. Usually always but I don't normally invite the government into my house to verify and see what I'm up to just like they don't tell me what they're up to.

Like you, I worked for a law enforcement agency (state) for over 30 years and I never had a problem with somebody who was following the law. When it comes to your house, though, you're expected to prove with inspections that you are not a chronic law breaker? Sounds like an authoritarian Nazi state.

Anyway, if I were @tk3000 , I would put an AAV on there in a heartbeat. We never determined if @tk3000 was in a UPC or IPC code area but either way, I'd do it. Unless he is doing a kitchen remodel, tearing out the wall and installing an atmospheric vent is out of the question. Leaving the S Trap would keep me up at night.

I already mentioned several good reasons to use an AAV. Here are a couple more...

When we bought our current house in 2020, I noticed that our house (built in 1970) and many others in the area had drains going straight down through the floor (just like @tk3000). Many had no vent, others had a vent. I asked someone why the drains didn’t go through the wall like I was used to seeing. The answer was because of freezing temps... and it’s easier to go straight down than through the wall. It doesn’t freeze here very often but when it does, it always catches people unprepared. If you live in Montana, you probably have it figured out better than we do down here in the South. Going straight down through the floor presents a small problem for venting. It can be done though. It’s a great reason for an AAV.

The other thing for me was, when I remodeled our kitchen, I discovered there was an original kitchen drain made out of galvanized pipe than had a traditional trap arm going into the wall. The galvanized trap arm was completely corroded through. Someone (previous to us) had bypassed it with PVC and ran the drain down through the floor via a S Trap. But because there is a window above the kitchen sink, the original galvanized trap arm had to cut through numerous studs and even the king stud and jack stud surrounding the window to get to a place where a vertical vent could be located. I know this is common and just the way it was done for many decades since indoor plumbing became a thing. I don't like it though. Cutting through all those studs doesn't make much sense to me. It's a case of plumber verses framer because I doubt the framers like it much either. So, going straight down through the floor with the drain makes sense for three reasons. 1) freeze protection 2) Ease of install and maintenance 3) less framing destruction. Going straight down with the drain presents a problem for venting though. An AAV solves this problem.

The same situation present in the kitchen (s-trap) is taking place in the bathroom upstairs in my condo in Lansing, MI (I currently in Fort Wayne, IN). So, since I am already at it; will do the same thing to the bathroom upstairs (add sanitary tee, extra pvc pipe, do the necessary adjustments along with the slip joint parts). The thing is that the whole complex (condominium) is like that, and I never had any issues with it (gurgling noise, odors, draining issues, etc). But it is not a job or expensive job, so will do it just for kicks and avoid any issues with the sale.

The following is the air admittance valve I am planning to use:

https://www.amazon.com/gp/product/B0069KCZO4/ref=ox_sc_saved_title_2?smid=ATVPDKIKX0DER&psc=1

The Michigan Plumbing Cod 2021 is based on the IPC 2021 (IPC 20210), according to a website:

Official title: Michigan Plumbing Code
Effective dates: March 12, 2024 - Present
Adopts with amendments: International Plumbing Code 2021 (IPC 2021)

Would the install of an AAV be compliant with the IPC in this situation?

Currently, my “new” house (where I am living) in Fort Waye, IN, is having some venting issues sometimes as well; in the form of gurgling noises. I still have to go to the roof and take a look at the venting stack (maybe inspects it with a borescope camera at some point). But, I suspect that some of the fixtures are not properly vented (a wet vent).

“Like you, I worked for a law enforcement agency (state) for over 30 years and I never had a problem with somebody who was following the law. When it comes to your house, though, you're expected to prove with inspections that you are not a chronic law breaker? Sounds like an authoritarian Nazi state. “

=> I totally agree with that sentiment.

"When we bought our current house in 2020, I noticed that our house (built in 1970) and many others in the area had drains going straight down through the floor (just like @tk3000). Many had no vent, others had a vent. I asked someone why the drains didn’t go through the wall like I was used to seeing. The answer was because of freezing temps... and it’s easier to go straight down than through the wall. It doesn’t freeze here very often but when it does, it always catches people unprepared. If you live in Montana, you probably have it figured out better than we do down here in the South. Going straight down through the floor presents a small problem for venting. It can be done though. It’s a great reason for an AAV."

=> Ron, it is odd that in the mid and late 70s S-Traps were still largely deployed in new construction given that they are notorious to be problematic since long before.

Thanks!

 

[PJB12]

The Michigan Plumbing Cod 2021 is based on the IPC 2021 (IPC 20210), according to a website:

Official title: Michigan Plumbing Code
Effective dates: March 12, 2024 - Present
Adopts with amendments: International Plumbing Code 2021 (IPC 2021)

Would the install of an AAV be compliant with the IPC in this situation?


Thanks!

Yes, absolutely as long as Lansing doesn't have their own code superseceding. Many Michigan cities have such codes. Detroit won't allow AAV unless the diaphragm is above the flood rim. Interestingly, they still allow BOCA vents.

Per IPC (if I remember correctly) the entire valve has to be 4" above the horizontal and 6" above insulation. It also has to be tilted vertically plumb or within a certain amount of vertical. I think 15 degrees is maximum, but can't remember for certain

The valve has to be sized for the DFU count and should meet ASSE 1050 & 1051 or NSF 14 or one of the other approved standards. Oatey all do, as do all Studor. Imports, not so much.

 

[tk3000]

Yes, absolutely as long as Lansing doesn't have their own code superseceding. Many Michigan cities have such codes. Detroit won't allow AAV unless the diaphragm is above the flood rim. Interestingly, they still allow BOCA vents.

Per IPC (if I remember correctly) the entire valve has to be 4" above the horizontal and 6" above insulation. It also has to be tilted vertically plumb or within a certain amount of vertical. I think 15 degrees is maximum, but can't remember for certain

The valve has to be sized for the DFU count and should meet ASSE 1050 & 1051 or NSF 14 or one of the other approved standards. Oatey all do, as do all Studor. Imports, not so much.

I did a recursive online search of what BOCA vent means and found some conflicting information. Is BOCA venting another type of venting pertaining to a different plumbing code (“The BOCA National Plumbing Code”)?

“Per IPC (if I remember correctly) the entire valve has to be 4" above the horizontal and 6" above insulation. It also has to be tilted vertically plumb or within a certain amount of vertical. I think 15 degrees is maximum, but can't remember for certain “

=> Are the 4” above the horizontal and 6” above insulation the minimums? Could it be, like, 6” above horizontal and 6” above insulation? What does insulation means in this context?

 

[tk3000]

At my house, I'll call for inspection if it's something that could cause an insurance company rejection of a claim, such as electrical or gas. Truthfully, I used to call for inspection to have a second set of "expert" eyes on the project. But, the "expert" part went out the window long ago. Believe it or not, where I live the electrical inspectors do not have to be electricians.


Here in southeast Michigan we get freezing temps from late October to about mid march. The part of my house with the kitchen was built in about 1900. It has little wall insulation and certainly no wind break under the siding. Plumbing was added to the house in the 20's.

The galvanized sink drain used to go into the wall and down. That part of the kitchen is on a 24" cantilevered section that is hanging outside in mid air. Hoarfrost would close it often. Very often! I re-piped to have the required horizontal trap arm distance, then down. The horizontal under the floor still is in the overhang, but hasn't closed (yet...). I suppose being PVC instead of galvanized helps a bit.

The then existing galvanized water lines used to go into the wall and down. They'd freeze daily, probably because they were in the cantilevered section.

My solution was to bring the water lines up from the basement as close to the front of the cabinet as possible (still barely in the overhang). I ran them as close to the floor of the cabinet that coper 90's would allow, then to the back of the cabinet and up to angle stops.

But, what does one do with two copper pipes on the floor of the cabinet? I put drawer runner slides on the sides of the cabinet all the way to the bottom. I made a short sided drawer the size of the cabinet floor. It sure is convenient to pull the drawer out to get to stuff. The downside it that I'll have to take apart my masterpiece to remove the cabinet and I lost about 1" of height in the cabinet.

The west wall of the house had two copper tubing runs up the wall to the second floor for heat. They would also freeze just about every day. I re-ran that zone up an inside wall. The abandoned copper tubing now are chases for telephone, ethernet and antenna wires.

Weird size, too. The OD of the tubing is 1.295" and the walls are far heavier than Type L. The fittings are interesting, too. They are hand-hammered flare to NPT like those we used on lead water lines. It must be from very early in the copper days.


The age-old argument on job sites! I guess the plumber won that one.

Plumbers always win. I wired a new construction mansion as a "pressured into it job" for a big shot at work. (I don't do residential except for friends or forced labor. Worse was that this was clock hours. Not my contractor rate.)
The building was specified all EMT conduit above grade. Walls (exterior and partition) were foam block with concrete fill and the floors on all 3 levels were poured. My rough-in had the green tag & was ready for devices and the elevator guys. Then things went backwards. Really backwards.

The plumber ran a 4" stack exactly on-center in front of the load center, 2" in front of the door. I couldn't open it to access a breaker, let alone get the job to pass. I was there long before plumbing rough-in, not even his underground was roughed. A couple of high 22-/12's would have shifted the stack plenty far away in this 14 foot tall basement.

In the end, he won. I moved the load center, reworked and rewired the service entrance and re-worked all of the conduits I'd already installed- plus spent a day on the rough re-inspect.
I was so happy to get out and go back to my nice, quiet and peaceful industrial work!

“Here in southeast Michigan we get freezing temps from late October to about mid march. The part of my house with the kitchen was built in about 1900. It has little wall insulation and certainly no wind break under the siding. Plumbing was added to the house in the 20's.”
=> That’s an old house! Must have good bones!


“The building was specified all EMT conduit above grade. Walls (exterior and partition) were foam block with concrete fill and the floors on all 3 levels were poured. My rough-in had the green tag & was ready for devices and the elevator guys. Then things went backwards. Really backwards. “

=> I lived in countries where wood framing is not a thing, it is all made of concrete and bricks; the floors, the interior walls, the exterior walls. Sometimes (especially in the country side), the roof framing is made out of lumber.

Paul, do you do work more with light or heavy industrial sites? Some of these industrial facilities must use electric power systems at very high voltages.

 

[PJB12]

I did a recursive online search of what BOCA vent means and found some conflicting information. Is BOCA venting another type of venting pertaining to a different plumbing code (“The BOCA National Plumbing Code”)?

“Per IPC (if I remember correctly) the entire valve has to be 4" above the horizontal and 6" above insulation. It also has to be tilted vertically plumb or within a certain amount of vertical. I think 15 degrees is maximum, but can't remember for certain “

=> Are the 4” above the horizontal and 6” above insulation the minimums? Could it be, like, 6” above horizontal and 6” above insulation? What does insulation means in this context?

I think I accidentally used the generic term when I wrote "Boca" Vent". Kind of like saying Kleenex for facial tissue. Being from the way back days, I can't think of the technical name. They pre-date the term (and mechanics of) a modern Air Admittance Valve.

Boca Vents were the first air admittance valves. Specifically they were invented for beauty shops with rows of sinks in the middle of a room, or so the legend goes. Those have a thin rubber disc that is held against a seat by a light spring. When the drain enters a partial vacuum, the diaphragm pulls down to let air in. When the vaccum subsides, the spring pushes the flap up. They are recognized by the obnoxious burping noise when sink drains quickly. I think that diaphragm type is still sometimes used in motor homes.


How High?
The (modern) AAV certainly can be as high as you wish as long as it is accessible for inspection and it can get air. Sometimes they get installed in an accessible attic when roof penetration for a standard VTR is impractical.

About Accessibility:
Before codes changed and they always had to be above the flood rim. Therefore the devices often used to be in walls with a heating return air register over the opening in the wall for air and for inspection. For mid-room sinks, often a tall backsplash with a removable panel was where the vent was installed. My shop sink has one flush with the deck of the sink. The very deep sink's deck is far more than 4" above the pipe. (Not to code here, but to code in the real world)

I think that "above the flood rim" rule goes back to when the only type were those described in a paragraph above. They are prone to having debris washing up to the diaphragm or spring, preventing closing. Unfortunately, some codes still stick to it. And some prohibit AAV devices entirely.

Above insulation refers to two scenarios: First, it was for when the valve was in an attic, above a drop ceiling or other space with batt insulation. Six inches was so that when the batts de-compressed, the valve would still be above them. (New construction in mind)

Later, it also applied to sink drains meeting ADA requirements. Those have insulation on the exposed drain parts so that someone in a wheelchair or scooter won't burn her or his legs. Measure from the top of the insulation on the trap arm. I don't think six is needed because the insulation is covered by a shell, but what do I know?

 

[Ron Van]

Currently, my “new” house (where I am living) in Fort Waye, IN,

I was born in Angola, Indiana while my Dad was attending Tri-State College. I tell people I was born in Angola and they usually think of a country in Africa rather than a small city in Indiana.

=> Ron, it is odd that in the mid and late 70s S-Traps were still largely deployed in new construction given that they are notorious to be problematic since long before.

Actually, the original build in 1970 had a galvanized drain that had an open air vent. The galvanized trap arm rotted and was bypassed with a PVC S Trap going straight down through the floor and reconnected with the original drain in the crawlspace.

From the crawlspace you can see the original galvanized drain that was going through the exterior wall and the bypass PVC drain going through the floor. I took both of them out when I remodeled the kitchen and repaired the rotted subfloor (due to the leaking trap arm and numerous other leaks).



Here is the original galvanized trap arm. The plumber that installed the galvanized trap arm when the house was built in 1970 completely destroyed the integrity of the window king and jack studs. It's not a mystery why the sub floor was rotted out.


Here's the repair I did under the kitchen sink area. Because the old sink cabinet covered the floor and wall (and the trap arm was in the wall), the previous owners didn't notice the leak in the rotted trap arm until a lot of damage was done. I guess this is another reason why having the drain go down through the floor instead of in the wall is a good idea. . .you can see if it leaks. This was our kitchen during Thanksgiving and Christmas of 2021.


The original trap arm had to cut through the three studs on the right side of the window and then the vent went up the stud bay to the right of the window. I had to replace all the wood in that area.


I used Kerdi tape on the edges and corners (like a shower pan), in the kitchen sink area, covered with Aqua Defense (Lowes brand of Red Guard) when I put the kitchen sink area back together. Water won't penetrate that subfloor again!

That piece of wall that is cut out on the right side of the picture was another part of the reno. I just got my wife, Ruby, to lift a beam up there for me. She's much stronger than she looks!



Here's what it looks like these days.





Here's a picture of my AAV installation. I used a Studor, mostly because that's what they had at my local Builder's supply. I installed a plastic tray in the bottom of the cabinet because I'm paranoid about water leaks. Hopefully, if the Studor fails, it will be noticeable and I'll just unscrew it and put a new one on.



We have a single bowl sink so the plumbing is a little easier.

 

[PJB12]

You sure did a great job on the kitchen work, Ron Van!
It's amazing how some tradespeople hack away at framing "because it's easier".
I loved seeing your nail plates over wires that people skip or forget.

Mapei's Aqua Defense, to me is leaps and bounds better than Red Guard. It's so very easy to work with, has nearly zero VOC and is brutally tough when dry. It dries fast, too. I've put the second coat, mixed the mud and by the time the thinset has slaked, the Aqua Defense is ready for tile.

 

[tk3000]

I was born in Angola, Indiana while my Dad was attending Tri-State College. I tell people I was born in Angola and they usually think of a country in Africa rather than a small city in Indiana.


Actually, the original build in 1970 had a galvanized drain that had an open air vent. The galvanized trap arm rotted and was bypassed with a PVC S Trap going straight down through the floor and reconnected with the original drain in the crawlspace.

From the crawlspace you can see the original galvanized drain that was going through the exterior wall and the bypass PVC drain going through the floor. I took both of them out when I remodeled the kitchen and repaired the rotted subfloor (due to the leaking trap arm and numerous other leaks).

View attachment 33782

Here is the original galvanized trap arm. The plumber that installed the galvanized trap arm when the house was built in 1970 completely destroyed the integrity of the window king and jack studs. It's not a mystery why the sub floor was rotted out.
View attachment 33785

Here's the repair I did under the kitchen sink area. Because the old sink cabinet covered the floor and wall (and the trap arm was in the wall), the previous owners didn't notice the leak in the rotted trap arm until a lot of damage was done. I guess this is another reason why having the drain go down through the floor instead of in the wall is a good idea. . .you can see if it leaks. This was our kitchen during Thanksgiving and Christmas of 2021.

View attachment 33783
The original trap arm had to cut through the three studs on the right side of the window and then the vent went up the stud bay to the right of the window. I had to replace all the wood in that area.

View attachment 33784
I used Kerdi tape on the edges and corners (like a shower pan), in the kitchen sink area, covered with Aqua Defense (Lowes brand of Red Guard) when I put the kitchen sink area back together. Water won't penetrate that subfloor again!

That piece of wall that is cut out on the right side of the picture was another part of the reno. I just got my wife, Ruby, to lift a beam up there for me. She's much stronger than she looks!

View attachment 33790

Here's what it looks like these days.
View attachment 33789

View attachment 33788


Here's a picture of my AAV installation. I used a Studor, mostly because that's what they had at my local Builder's supply. I installed a plastic tray in the bottom of the cabinet because I'm paranoid about water leaks. Hopefully, if the Studor fails, it will be noticeable and I'll just unscrew it and put a new one on.

View attachment 33792

We have a single bowl sink so the plumbing is a little easier.

View attachment 33793

“I was born in Angola, Indiana while my Dad was attending Tri-State College. I tell people I was born in Angola and they usually think of a country in Africa rather than a small city in Indiana.”

==> That’s cool. Few years ago, I was considering buying a house in Angola.

It is funny that you mentioned Angola, though, because I have a whimsical story related to Angola. But first, a little backdrop of my current situation: Lately, my elderly mother is staying with me which is a blessing, but also very complicated for me at this time because I have to travel often and have to deal with many different problems and issues; as a result, I am often meandering through those issues, instead of solving them. But, back to the story. Often, I drive with her from Fort Wayne, IN, to Lansing, MI (and vice-versa) and as part of our route (I-69) we pass next to Angola. She was surprised when she saw the signs for the city of Angola the first time, then I told her most of the population of Angola came from the country of Angola back in the early 1900s and that they preserved all their culture, traditions and religious rituals (she is from Argentina and my father is from the US [but he worked in Brazil for an oil company], and they both lived in Brazil for many years; a State in Brazil with a large African heritage from Angola). Needless to say, she is very intrigued by it, and whenever I drive north or south of the I-69 with her, she keeps asking me to take the exit to Angola.

“Actually, the original build in 1970 had a galvanized drain that had an open air vent. The galvanized trap arm rotted and was bypassed with a PVC S Trap going straight down through the floor and reconnected with the original drain in the crawlspace.

From the crawlspace you can see the original galvanized drain that was going through the exterior wall and the bypass PVC drain going through the floor. I took both of them out when I remodeled the kitchen and repaired the rotted subfloor (due to the leaking trap arm and numerous other leaks).”

=>Yeah, that looks badly rotten. At the end of the line, in my condo in Lansing, there are large cast iron pipes which goes underground. In the past, I used to use bleach a lot to sanitize toilets, bathtubs, etc; which really would accelerate the corrosion process. Now, I avoid bleach going to drain as much as possible.

You undertook lots of work! Very well done, it turned out great!

I got the “Oatey Sure-Vent 1-1/2 in.–2 in. 160 Branch, 24 Stack DFU Air Admittance Valve with White PVC Sch. 40 Adapter” and all the supplies needed. It seems that this aav can be used with both 1 ½” and 2” pvc pipe. It seems a straightforward job; the only problem is that the pvc pipe protruding from the floor has a couple and it is kind of short, so I may have to removed disposer to better cut it. Another issue, I am considering is that the plumbing inside the walls and main plumbing is the responsibility of the HOA; so, even though I may be trying to improve things, they may consider it wrong for the wrong reasons.

 

[tk3000]

I think I accidentally used the generic term when I wrote "Boca" Vent". Kind of like saying Kleenex for facial tissue. Being from the way back days, I can't think of the technical name. They pre-date the term (and mechanics of) a modern Air Admittance Valve.

Boca Vents were the first air admittance valves. Specifically they were invented for beauty shops with rows of sinks in the middle of a room, or so the legend goes. Those have a thin rubber disc that is held against a seat by a light spring. When the drain enters a partial vacuum, the diaphragm pulls down to let air in. When the vaccum subsides, the spring pushes the flap up. They are recognized by the obnoxious burping noise when sink drains quickly. I think that diaphragm type is still sometimes used in motor homes.


How High?
The (modern) AAV certainly can be as high as you wish as long as it is accessible for inspection and it can get air. Sometimes they get installed in an accessible attic when roof penetration for a standard VTR is impractical.

About Accessibility:
Before codes changed and they always had to be above the flood rim. Therefore the devices often used to be in walls with a heating return air register over the opening in the wall for air and for inspection. For mid-room sinks, often a tall backsplash with a removable panel was where the vent was installed. My shop sink has one flush with the deck of the sink. The very deep sink's deck is far more than 4" above the pipe. (Not to code here, but to code in the real world)

I think that "above the flood rim" rule goes back to when the only type were those described in a paragraph above. They are prone to having debris washing up to the diaphragm or spring, preventing closing. Unfortunately, some codes still stick to it. And some prohibit AAV devices entirely.

Above insulation refers to two scenarios: First, it was for when the valve was in an attic, above a drop ceiling or other space with batt insulation. Six inches was so that when the batts de-compressed, the valve would still be above them. (New construction in mind)

Later, it also applied to sink drains meeting ADA requirements. Those have insulation on the exposed drain parts so that someone in a wheelchair or scooter won't burn her or his legs. Measure from the top of the insulation on the trap arm. I don't think six is needed because the insulation is covered by a shell, but what do I know?

It is clear now! Thanks for your thorough explanation and insights!

I made it to Lansing, but something did crop up and will have to return tonight to Fort Wayne. I will have to look into doing once I return (maybe one or two weeks). In the meantime, I found another issue with the bathtub (for another thread).

 

[Ron Van]

It is funny that you mentioned Angola, though, because I have a whimsical story related to Angola

. She was surprised when she saw the signs for the city of Angola the first time, then I told her most of the population of Angola came from the country of Angola back in the early 1900s and that they preserved all their culture, traditions and religious rituals (she is from Argentina and my father is from the US [but he worked in Brazil for an oil company], and they both lived in Brazil for many years; a State in Brazil with a large African heritage from Angola). Needless to say, she is very intrigued by it, and whenever I drive north or south of the I-69 with her, she keeps asking me to take the exit to Angola.

That’s an amazing piece of historical knowledge that I had no idea of! I was born there but my family moved to Elkhart, Indiana after my dad graduated from Tri State. I lived in Elkhart until 1978 when I moved to California. Ruby and I moved to Alabama 4 years ago.

Another issue, I am considering is that the plumbing inside the walls and main plumbing is the responsibility of the HOA; so, even though I may be trying to improve things, they may consider it wrong for the wrong reasons.

a long time ago, my wife and I owned a condo that I bought for my mother so she could move from Indiana to California so she could be closer to my young (at the time) kids. I was on the condo homeowner’s association board as the treasurer. That board had a pitbull of a president that had more power than I assumed possible. She was able to get a homeowner evicted from his own condo for breaking the association’s bylaws. He was a bad person and a chronic rule breaker but the thing that got him evicted was he had an American flag in a bedroom window rather than an acceptable curtain.