Expansion tank install

TresK3

Member
Jul 12, 2007
137
Cincinnati, Ohio
Just got the new hybrid hot water heater AND an expansion tank (the current system doesn't have one). A couple of questions about installing the expansion tank.

1) The (limited) instructions from the tank show it vertical with the top up. It also shows "optional" positions as verticle with the top down or horizontal. Only the horizontal position mentions supporting the tank. If I brace the copper pipe on the ceiling (copper u-straps into a 1x4 between two joists) can I just "hang" the expansion tank from this? Or do I need some sort of support or bracket holding the tank up?

2) There appears to be sufficient room above the water heater to fit the expansion tank vertically, with about 2-3" on both top and bottom. This would make the install a bit neater and easier, since I've got shelves on either side of the space. Is there any problem with putting it directly above the water heater, hanging down?

Thanks!
 

maple1

Minister of Fire
Sep 15, 2011
10,485
Nova Scotia
I think I would hang/support the tank itself, vs. hanging it off piping, and likely orientation does not matter.

But are you sure you need one?
 

johneh

Minister of Fire
Dec 19, 2009
2,865
Eastern Ontario
I am curious why do you need an expansion tank?
How hot are you heating this water to?
In my 70 some years I have never seen an expansion tank on a water heater.
 

TresK3

Member
Jul 12, 2007
137
Cincinnati, Ohio
I am curious why do you need an expansion tank?
How hot are you heating this water to?
In my 70 some years I have never seen an expansion tank on a water heater.
The system maybe closed - I suspect there's a backflow preventer at the meter. When the water heats up it will expand, and needs somewhere to go. I'm not certain of the code where I live, but that seems to be standard in a lot of places.
 

TresK3

Member
Jul 12, 2007
137
Cincinnati, Ohio
I ended up installing it horizontal, with two straps looped to the ceiling. It's not cinched down tight, but if there's any weight in it, it should snug up a bit.
 

Highbeam

Minister of Fire
Dec 28, 2006
17,312
Mt. Rainier Foothills, WA
The system maybe closed - I suspect there's a backflow preventer at the meter. When the water heats up it will expand, and needs somewhere to go. I'm not certain of the code where I live, but that seems to be standard in a lot of places.
You’re right. For decades we’ve been installing meter setters that include a check valve. It really ticks off the homeowners when doing this causes their water heater to leak from the TPV. Just do it.

Oh and be sure to set the air pressure properly.
 

begreen

Mooderator
Staff member
Nov 18, 2005
82,999
South Puget Sound, WA
I am curious why do you need an expansion tank?
How hot are you heating this water to?
In my 70 some years I have never seen an expansion tank on a water heater.
Likewise. And never had an issue in any house. That said some municipal systems require them.
 
Last edited:

TresK3

Member
Jul 12, 2007
137
Cincinnati, Ohio
Put it in horizontally, hanging from the ceiling.

Bought a new pressure guage and the pressure at the laundry sink is 70 PSI. The tank is 65, based on my tire pump. For some reason, I can't get the pump to budge when I try to add more air. Possibly because it's on top of a ladder and I'm on the ground. :)
Is that close enough, or do I need to worry about the extra 5 lbs.?

Also, do I need a pressure-reducing valve for the whole house? We don't seem to have excessive pressure, but most of the faucets and shower heads are low-flow.
 

maple1

Minister of Fire
Sep 15, 2011
10,485
Nova Scotia
That's more pressure than I'm used to, and likely more than I'd be comfortable with. But have always been on a well.

Air pressure in the tank should have been checked when it was empty of water and before it was hooked to the system. With a well and pump, you'd set it around the cut in pressure of the pump. Or maybe a pound or 2 less. For me that was 18psi. If your supply is a constant 70 (that seems like a lot still to me but not sure what a typical municipal supply is), then thinking 65 before installing would be ballpark.
 

Highbeam

Minister of Fire
Dec 28, 2006
17,312
Mt. Rainier Foothills, WA
That's more pressure than I'm used to, and likely more than I'd be comfortable with. But have always been on a well.

Air pressure in the tank should have been checked when it was empty of water and before it was hooked to the system. With a well and pump, you'd set it around the cut in pressure of the pump. Or maybe a pound or 2 less. For me that was 18psi. If your supply is a constant 70 (that seems like a lot still to me but not sure what a typical municipal supply is), then thinking 65 before installing would be ballpark.
Expansion tanks like this have a different function than well expansion/bladder tanks. You don't set them based on well cut in pressure because these tanks are supposed to stay full of air until there is an "overpressure" event. A regular well bladder tank is designed to fill and drain with each pump cycle so the air pressure needs to be much lower. If your static is 70 then set the little expansion tank to 70. No less. You only want the expansion tank in the game when needed. These little expansion tanks usually come with just 40 psi in them. You'll need to add air to get to 70.

http://www.americanwaterheater.com/media/22209/exptank.pdf

Oh, and if you are on a well (like I am) you set the little expansion tank's air pressure to be the max normal pressure of the system which is the pump off pressure. I have a 40/60 pressure switch on my well so the little expansion tank gets 60 psi.
 

johneh

Minister of Fire
Dec 19, 2009
2,865
Eastern Ontario
Oh, and if you are on a well (like I am) you set the little expansion tank's air pressure to be the max normal pressure of the system which is the pump off pressure. I have a 40/60 pressure switch on my well so the little expansion tank gets 60 psi.
If he were on a well he would not need the little expansion tank
The well tank would take care of any expansion and there would be no check valve
 

Highbeam

Minister of Fire
Dec 28, 2006
17,312
Mt. Rainier Foothills, WA
If he were on a well he would not need the little expansion tank
The well tank would take care of any expansion and there would be no check valve
You’re right in theory but if there is a valve between the well it and and the water heater like many folks have at the cold inlet to the water heater then your well tanks are not going to help and something else will give up the pressure if that valve is operated.

Codes are put in place for these oops type of situations.
 

brenndatomu

Minister of Fire
Aug 21, 2013
5,070
NE Ohio
That's more pressure than I'm used to, and likely more than I'd be comfortable with. But have always been on a well.

Air pressure in the tank should have been checked when it was empty of water and before it was hooked to the system. With a well and pump, you'd set it around the cut in pressure of the pump. Or maybe a pound or 2 less. For me that was 18psi. If your supply is a constant 70 (that seems like a lot still to me but not sure what a typical municipal supply is), then thinking 65 before installing would be ballpark.
70 is not that uncommon on city water...the local system has an area of town that runs 110...they had to put regulators in with the water meters there!
 

maple1

Minister of Fire
Sep 15, 2011
10,485
Nova Scotia
Expansion tanks like this have a different function than well expansion/bladder tanks. You don't set them based on well cut in pressure because these tanks are supposed to stay full of air until there is an "overpressure" event. A regular well bladder tank is designed to fill and drain with each pump cycle so the air pressure needs to be much lower. If your static is 70 then set the little expansion tank to 70. No less. You only want the expansion tank in the game when needed. These little expansion tanks usually come with just 40 psi in them. You'll need to add air to get to 70.

http://www.americanwaterheater.com/media/22209/exptank.pdf

Oh, and if you are on a well (like I am) you set the little expansion tank's air pressure to be the max normal pressure of the system which is the pump off pressure. I have a 40/60 pressure switch on my well so the little expansion tank gets 60 psi.
Yes, correct. I derailed myself from the get go with that one.
 
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