# Domestic Expansion Tank location



## mccmech (Jul 6, 2011)

Soooo, what's the consensus of the bright minds on this site, shall a domestic water expansion tank be I stalled on the cold/ inlet side of a water heater, or shall it be I stalled on the hot/ outlet side of said water heater? I realize there has been discussion, many moons ago.


----------



## jmc12185 (Aug 27, 2013)

Cold water . Always. Close to the heater.


----------



## Tommy plumber (Feb 19, 2010)

Cold side.


----------



## AWWGH (May 2, 2011)

Cold


----------



## KoleckeINC (Oct 22, 2011)

I had an inspector ask for one even though it wasn't a closed system. So I put a double check at the meter and he was like-why'd ja do that? 
I have no idea why it goes on the cold side between the valve and the tank.


----------



## rjbphd (Feb 5, 2010)

KoleckeINC said:


> I had an inspector ask for one even though it wasn't a closed system. So I put a double check at the meter and he was like-why'd ja do that?
> I have no idea why it goes on the cold side between the valve and the tank.


Huh??? Its a CLOSED system when none of the plumbing fixtures are being used...


----------



## Nealfromjpt (Oct 10, 2012)

cold side always


----------



## KoleckeINC (Oct 22, 2011)

rjbphd said:


> Huh??? Its a CLOSED system when none of the plumbing fixtures are being used...


I thought it was uh closed system when a you donna pay a your bill


----------



## Plumbbum0203 (Dec 14, 2011)

Still could be open. Our main water lines are not protected by a check valve or back flow. If pressure exceeds incoming from main it will push back Into the main. We put a tank on the cold side because the hot is already expanded.


----------



## plumbdrum (Nov 30, 2013)

Up 3' above the tank with the T&P valve👍👍


----------



## PLUMBER_BILL (Oct 23, 2009)

rjbphd said:


> Huh??? Its a CLOSED system when none of the plumbing fixtures are being used...




Hey folding rule all your properties have backflow valves on the water service, re green above? System would be open with no checks or B/F 

Original post -- cold side but why must the thermal tank be close to the water tank?
I have heard that before ... Just wondering


----------



## kimo (Jul 22, 2011)

Expansion tank to be fitted close to the heater so that:

1. anyone coming later can instantly see that you have one installed
2. like the P&T in the top 6" of the heater, proximity will mean a quick response
Anyway, thats what i've been told.

AAMOI: i've dug up PRV's on the service way out near the water meter - just so happened we were changing the service and the old , typically by now useless, PRV came up with it.
We replaced the PRV set the pressure and buried it again. 
Bad practice but thats what we were told to do.


----------



## kimo (Jul 22, 2011)

I've just tried to edit the above post but after editing i dont see how to re-post it?
Can someone help me?


----------



## dorian_grey (Sep 9, 2013)

I install them just downstream of my testable backflow devices as often as possible so when I do a backflow test they are checked as well.


----------



## Plumbbum0203 (Dec 14, 2011)

What do you guys set your tank pressure to? We set them equal to the house pressure. We have to do that and write the house and tank psi on it or it fails.


----------



## Plumber patt (Jan 26, 2011)

Plumbbum0203 said:


> What do you guys set your tank pressure to? We set them equal to the house pressure. We have to do that and write the house and tank psi on it or it fails.


We set them to 60% of static pressure. That way when the thermal expansion occurs it will cushion into the tank. 

And yes its an "open" system when fixtures are being used. But during the night when they are not being used and your hwt fires, then its a closed system with a premise backflow.


----------



## plumberkc (Jun 23, 2011)

Has anybody ever seen an expansion tank more than 5 years old that wasn't just full of water? I tell everybody that you have to recharge them every year and replace them after 5. I also have never seen one installed with a di-electric Union.


----------



## Plumbbum0203 (Dec 14, 2011)

We use di electric unions on them. You might get rheemed around here for using di electric unions.they fill up with water after a year or so. On many occasions I have tried to bleed some air out and was hit with water.


----------



## wyrickmech (Mar 16, 2013)

Cold side always most tanks are not rated for the heat.


----------



## sparky (Jan 8, 2014)

rjbphd said:


> Huh??? Its a CLOSED system when none of the plumbing fixtures are being used...


Uhhhh no,if no prv or check valve at meter then that is considered open system,meaning when wh is heating and water is expanding the excess pressure will become greater than what is in the main at the street allowing the excess pressure to flow back into the main taking care of thermal expansion


----------



## sparky (Jan 8, 2014)

PLUMBER_BILL said:


> Hey folding rule all your properties have backflow valves on the water service, re green above? System would be open with no checks or B/F
> 
> Original post -- cold side but why must the thermal tank be close to the water tank?
> I have heard that before ... Just wondering


While it is standard practice to install exp. tank near the water heater on the cold water side,it is just fine to install that exp tank ANYWHERE in the cold water line from where it enters the blding to the heater,it will do its job anywhere in this cold water line


----------



## sparky (Jan 8, 2014)

Plumbbum0203 said:


> What do you guys set your tank pressure to? We set them equal to the house pressure. We have to do that and write the house and tank psi on it or it fails.


You are correct,but I just air them up to 70-75lbs since the max is 80psi,I figure that way I'm covered no matter what. I.e. Pressure surge or whatever might happen


----------



## Plumbus (Aug 4, 2008)

I put 'em where the manufacturer says to put 'em. If anything goes wrong, the first thing the lawyers check is compliance with the manufacturer's installation instructions.


----------



## MACPLUMB777 (Jun 18, 2008)

sparky said:


> Uhhhh no,if no prv or check valve at meter then that is considered open system,meaning when wh is heating and water is expanding the excess pressure will become greater than what is in the main at the street allowing the excess pressure to flow back into the main taking care of thermal expansion


That is unless the street pressure is higher then the relief valve ie 150 psi


----------



## Richard Hilliard (Apr 10, 2010)

The expansion tank on an open system is worthless. Expansion will follow the path back into the potable main water system .

Go watch the meter move back and forth while the heater heats.You will need some type of check valve or protection device to make it a closed system


----------



## KoleckeINC (Oct 22, 2011)

Richard Hilliard said:


> The expansion tank on an open system is worthless. Expansion will follow the path back into the potable main water system . Go watch the meter move back and forth while the heater heats.You will need some type of check valve or protection device to make it a closed system


I had an inspector make me put one in anyway. No explanation.


----------



## rjbphd (Feb 5, 2010)

KoleckeINC said:


> I had an inspector make me put one in anyway. No explanation.


Did the meter have PRV ?? If not, no need for exp tank..... if so, yep, gonna needs it... on one major house addition job, didn't install the exp tank.. inspector demanded one.. gave him a stink eye and asked him if he know any thing about private well system.. he proudly stated he didn't have to.. told him that he needs to leave and not to come back on this project .. got my failed inspection reversed..


----------



## KoleckeINC (Oct 22, 2011)

No prv. Maybe something to do with the new meter. So he told me to put an expansion tank in. And I assumed he wanted a double check also. Nope, waste of 90$. Oh well-I got paid for the job and didn't dwell on it.


----------



## rjbphd (Feb 5, 2010)

KoleckeINC said:


> No prv. Maybe something to do with the new meter. So he told me to put an expansion tank in. And I assumed he wanted a double check also. Nope, waste of 90$. Oh well-I got paid for the job and didn't dwell on it.


With new meter install.. now comes with built in checkvalve... hence, the exp tank needed.. when replacing young water heaters installed by others.. I always look for the meter shut off first to see if the exp tank needed or not..


----------

