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confusedplus 09-06-2011 10:30 AM

Excesssive Sewer Line Downslope
I'm planning to install a convenience bathroom with a toilet and sink in my camp bunkhouse but the sewer line drop is roughly 5 feet vertical with a 40 foot run, far exceeding the 1/4" per foot sewer drainage recommended.
The bunkhouse is not used frequently and summer only but freezing needs to be a concern. The water supply line is no problem since the pipes are installed down sloped and blown down every year before vacating.
The 110v electrical system is 14 gauge wiring but do have 12 gauge wiring, if necessary, at the bunkhouse entrance.
I used a 12v macerator on my trawler for offshore use which may be a solution for pumping to my 1K gallon tank but need a 110v system. I also heard about a dry(?) or evaporative processing system. I would like to hook the sink to such unit if possible. The dry system would be handy for rare winter time convenience but no running water would be available except bucket-use if needed. The planned toilet is 1.6 gallons per flush. Thank you. :usa:

inspectorD 09-06-2011 01:53 PM

Sounds just like camp!!

The reasoning for the slope in the wasteline, is so the solids run downhill at the same rate as the fluids. To steep, and solids get left behind, to shallow and they don't run downhill very well with a 1.6gallon flush.
See if you can find an old toilet with a bigger tank = more water for the run.:welcome:

Redwood 09-07-2011 10:06 AM

It is fine to exceed 1/4" per foot pitch as that is the minimum, under some codes and pipe sizes 1/8" per foot is the minimum. The water outrunning the solids is a busted myth and is of no consequence.

As far as low flow toilets...
Lines that are heavily scaled or, leaking such as rotted out cast iron, clay with loose joints or, Orangeburg will tend to have problems with solids accumulating and dry-packing causing clogs. Also shallow pitch, flat pitch, or, bellied lines will tend to have problems especially when they are longer in length, strip malls are particularly vulnerable.....

inspectorD 09-07-2011 03:45 PM


Originally Posted by Redwood (Post 60773)
The water outrunning the solids is a busted myth and is of no consequence.

Thanks Redwood....I'm always the last to know.:o

Redwood 09-07-2011 03:52 PM

You get most of them! :beer:

A lot of plumbers don't know it either...
Don't feel bad...

confusedplus 09-08-2011 08:58 AM

Thanks, Redwood. Having not sailed down a sewer pipe :-), your response makes sense to me. As InspectorD kindly suggested, what are your thoughts for a higher volume toilet flush vs. my planned 1.6 gal flush? I plan to install a 90 degree sweep for a short entry into my septic tank or should I used a 90 degree with a cleanout plug. Also, I currently have a closeup 4" RV dump at the same planned tank entry point (4" vertical threaded 'T' fitting and a horizontal cleanout as well). Would this cause any restrictions if the sweep is tied into the RV threaded cleanout? The RV dump will be used for an infrequent RV tank drain with no concurrent use of the bunkhouse toilet. Yours, InspectorD's, or any comments are always appreciated.

Redwood 09-08-2011 02:54 PM

I would use a couple of 45's verses a 90.

As for the low flow toilet I wouldn't worry about it. Your line is new, in good condition, and adequately pitched, so there are no worries there...

As for freezing concerns the toilet will need it's tank dry and use non-toxic anti-freeze in the bowl to prevent the toilet from freezing and breaking.

confusedplus 09-08-2011 04:57 PM

Redwood, Your suggestion is well considered. I may have to use an elbow to get around a support. What minimum vent line diameter should I use? I talked to HomeDepot today and they told me that Maine does not allow selling new toilets with high water flush volume. My camp is on a lake so no worries about water availability. I have a low flush toilet in the camp with a sewer line drop about 1/2" per foot and no problems.
You didn't mention the "running thru my RV drain section to the septic tank." I wouldn't try it unless you thought otherwise and will relocate to the end septic entrance. Probably best to eliminate potential effluent hang-ups anyway. Thank you again. Regards, and maybe not so confused now, ConfusedPlus

Redwood 09-08-2011 07:07 PM

Yea 1.6 GPF is the law everywhere so any big water user would be a "good used toilet"

The next law we will see is 1.28 GPF toilets.... They are already required in some places...

Truth be told the early 1.6 GPF toilets stunk and many were just 3.5 toilets choked down...
It took a few years and Toto entering the market with toilets that worked before many companies got off their butts and went back to the drawing board essentially copying Toto's concept....

1.6 gallons dumped very quickly into the bowl worked!
Now 3" flush valves are quite common.

As for the RV Dump...
If you use the typical RV chemicals in your tank they are not septic tank friendly...
Also there tends to be more solids than waste so dumping can be problematic clog wise...
So No Chemicals and make sure there is plenty of water mied with the waste or, you'll have problems....

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