Exterior Tankless Water Heater Placement and Plumbing Questions

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harborremodel

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Hello All,

I'm considering transitioning our house to an exterior tankless water heater. My question is about running the cold / hot supply lines. To get from where the existing water heater is now to where i'd put the tankless is about a 25 foot run across the ceiling of my garage and then through an exterior wall where the heater would be mounted. I'm just wondering if i could skip that long run and instead tie into some bathroom supply lines that are pretty close to where the heater will be mounted on the exterior of the house. This bathroom is also very close to our master bath. These two bathrooms make up 95% of where showers are taken in our house.

Anyone have experience with these?
 
You can back feed the system so this would work. The question I would have though is what size pipes are feeding your water heater today and what size is feeding your bath? If you have 1/2" feeding the bathroom and 1" feeding your water heater you will notice the reduction in size. With a tankless water heater you want the shortest runs possible to reduce the wait time for hot water. Regular recirculation pumps defeat the savings of a tankless system. With tankless, if you need to install a recirculation pump for a long run you want an on-demand pump instead of one that cycles on and off all day based on water temperature and/or is controlled by a timer.
 
Don't forget that if you install a wall mounted tankless water heater, most models require that you have no window openings within 5' of each side of the TWH, due to a risk of carbon monoxide poisoning. Also, A good TWH will require a larger gas line that your normal appliances.

The above obviously only applies to natural gas. If you are only using electricity to run the TWH, I would not recommend this TWH at all.
 
havasu said:
Don't forget that if you install a wall mounted tankless water heater, most models require that you have no window openings within 5' of each side of the TWH, due to a risk of carbon monoxide poisoning. Also, A good TWH will require a larger gas line that your normal appliances.

The above obviously only applies to natural gas. If you are only using electricity to run the TWH, I would not recommend this TWH at all.
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Why would not recommend an electric one? I was thinking about getting one.:hide:
 
tuffy said:
Why would not recommend an electric one? I was thinking about getting one.:hide:
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You may need to double your house elec. service and notify your PoCo of your intentions.
 
Wuzzat? said:
You may need to double your house elec. service and notify your PoCo of your intentions.
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Oh ok I guess I will figure out some way to run gas service to it. shouldn't be to hard i have a plan in mine. we are allowed here to run new gas supply lines our selves.
 
tuffy said:
we are allowed here to run new gas supply lines our selves.
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Then maybe I shouldn't be afraid of doing my own gasfitting, provided I do the soap bubble test on each joint.

Can Due Diligence & textbooks make up for lack of experience?

A guy did his own gas dryer install and the whole house blew up at 3 A.M. His wife(girlfriend?) landed on the lawn complaining of shortness of breath.

Another time the gas company increased the pressure which overcame household safety devices.
A girl turned on a light switch.
They did find her legs relatively intact.

But, these ^ are
http://www.google.com/search?client=safari&rls=en&q="anecdotal+evidence"&ie=UTF-8&oe=UTF-8

Is the Missouri rate of gas explosions or fires, corrected for the number of households, above the national average?
Dunno'.

We need one of these books
https://www.amazon.com/dp/0071629696/?tag=skimlinks_replacement-20
specifically for DIYers.
 
Last edited by a moderator:
I believe that the pipes headed into the current water heater are 3/4 or 1". The proposed placement of the water heater on the exterior is clear of any windows in all directions for at least 8+ feet. Unfortunately our house has mostly PVC running through the walls but it does have copper lines where the current water heater is. The gas supply isn't an issue as the meter and the large feed line into the house and about 6-10 feet away.
 
You should be able to get away with 3/4 for the gas at that short a distance? What’s the total btu’s for all your gas appliances? If you get up over a certain amount you may need a larger capacity gas meter. It’s all about volume when going to a tankless, pressure should be a given from the utility, here in California it’s 7”w.c. Or 1/4 lb. I’m going back and forth with replacing my 40 gal tank with a tankless. There are advantages and disadvantages to both.
 
I had my natural gas company come out to do a pressure/volume check and provided input as to how big the gas line needs to be, before I installed the unit.

Water heater repair (11).jpg

Water heater repair (13).jpg
 
havasu said:
I had my natural gas company come out to do a pressure/volume check and provided input as to how big the gas line needs to be, before I installed the unit.
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Your profile says you like to work on jeeps!? Do you have some or one? I got bit by the bug about 5 years ago and loving it. Gonna be going to the Rubicon for my 2nd time this August.🤙
 
Yes, I'm a Jeep fanatic. CJ's, YJ's, and TJ's are my favorites. I've never been to the Rubi, but would love to one of these days!
 
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