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View Full Version : Expansion Tank for a Hot Water Heater



driem
10-23-2008, 09:08 AM
I am replacing a HWH and would like to add an expansion tank.

Question 1: I am not having problems with my current system, should I install one?

Question 2: The directions call for the tank to be mounted with the 3/4" fitting at the top or hanging by the fitting. I don't have the room to install per directions. Will it hender operations for the tank if I install it with the fitting on the bottom or "reverse" of the installation directions?

Thanks for your help....Dan
http://www.watts.com/prod_images/PLT.jpg (http://javascript<b></b>:popUp('/prod_images/hi-res/default.asp?imgId=852'))
http://www.watts.com/pdf/1915356.pdf

Cass
10-23-2008, 09:49 AM
Unless you have a Pressure Reducing Valve and / or a check valve you don't need one...

jadnashua
10-23-2008, 10:20 AM
The tank will work in any orientation. When it eventaully fails, if it is on top of the fitting rather than below it, you'll have a tank full of water trying to come out while you remove it. Depends on how well you can drain the pipe system as to how messy it would be.

But, as mentioned, unless you have or intend to install a PRV, or have a checkvalve in the system, you don't need one. Note, water districts may change their meters and the new ones could contain a checkvalve. Having an expansion tank won't hurt if you don't currently need one, but it won't buy you much except the expense to install.

Gary Swart
10-23-2008, 11:13 AM
When water heats it expands and needs somewhere to go. If you have an open system, that's one where you do not have either a PRV or a check valve in the meter, this expansion is absorbed by the city water main so you do not need an expansion tank. If you do have a PRV or check valve, this is called a closed system and the expansion has no place to go. This results in a very rapid pressure increase in the water heater and when the pressure reaches 150 psi, the T/P valve on your heater will open to relieve the excess pressure and prevent the heater from blowing up. :eek:

99k
10-23-2008, 05:07 PM
Do you have a well? If so, your present pressure tank will do the job.

hj
10-23-2008, 08:24 PM
YOu can install the tank in any direction, AS LONG as you support it by something other than the pipe connection.

http://www.watts.com/pdf/1915356.pdf

D'Brie
10-24-2008, 10:11 PM
When water heats it expands and needs somewhere to go. If you have an open system, that's one where you do not have either a PRV or a check valve in the meter, this expansion is absorbed by the city water main so you do not need an expansion tank. If you do have a PRV or check valve, this is called a closed system and the expansion has no place to go. This results in a very rapid pressure increase in the water heater and when the pressure reaches 150 psi, the T/P valve on your heater will open to relieve the excess pressure and prevent the heater from blowing up. :eek:

+1, This is the way I have been taught also.

drick
10-26-2008, 10:22 PM
Ok, I have a well and for various reasons I ended up installing a check valve after the pressure tank. Now I know I'm supposed to install an expansion tank and I will when I relocate my HW heater shortly (basement remodel), BUT I have never, not even once, seen my pressure gauge after the check valve read anything but a couple of PSI LOWER than the one located on the bladder tank manifold.

Like I said I'm still going to install the expansion tank because I know its supposed to be there and that heating water causes an increase in pressure, but just once I'd like to see it read even 5 PSI higher.

Cass
10-27-2008, 03:39 AM
Why is there a check valve there...I would remove it...that will be a lot easier and less expensive than a Exp. Tank.

nhmaster
10-27-2008, 04:11 AM
Prv, check valve, meter with check valve makes no difference. The code requires an expansion tank on all water heating pressure vessels.

Cass
10-27-2008, 04:29 AM
he is on a well...if he removes the check valve he has a very large expansion tank.

nhmaster
10-27-2008, 05:40 AM
The code does not say a well can be substituted for an expansion tank, besides which there is a foot valve down there somewhere.

Cass
10-27-2008, 07:41 AM
The code does not say a well can be substituted for an expansion tank, besides which there is a foot valve down there somewhere.

So you would put an expansion tank on a well system that had a direct, non checked, cold water path to the bladder tank from the water heater, that is what you would do?

Now hear me, I am asking you what you would do.

I have my hand on my helmet...getting ready...

hj
10-27-2008, 07:47 AM
It would be an unusual system if it had the foot valve between the tank and the water heater. The storage tank IS a large expansion tank, regardless of whether the codes call it that or not. The only way it does not meet some regulations is that it is not between the heater's cold water valve and the heater.

nhmaster
10-27-2008, 11:07 AM
I would absolutly put an expansion tank in. The code never asks for my opinion or how I feel about things. The words "shall" hold up in a court of law. Do I agree with putting a tank in? No, but because I am constantly worried about laibility (and so should you all be) I do everything to code. Then there's no questions, no arguments, no liability.

HJ there is a foot valve at the bottom of the well drop if it's a shallow well pump and a check valve on top of a submersible pump.

nhmaster
10-27-2008, 11:10 AM
In the same vain. There was discussion about whether or not the tank could go in the cold side. Since the manufacturers instructions say to install in the hot side, putting it in the cold side would be a code violation because the code says to follow the manufacturers directions if there is no specific code entry. I know it's all a huge pain in the &ss sometimes but the code is there to protect us from liability. Ha I'll bet most of you think the code is there to protect the consumer. And it does, but mostly, if we follow it to the letter we can not be held liable when something hit's the fan.

MACPLUMB 777
10-27-2008, 03:24 PM
Hey N.H. Master i usually agree with what you are posting,
but i think on this one you had better go back and reread
the mfg's instructions about installing tank on cold side
because in all my experience reading install directions and water
heater mfg's install diagrams the expansion tank goes on the cold side between the shut off valve and the water heater

and i agree with the liability factor but if someone had a well tank i would not automatically assume they needed a expansion tank,
and if i had a question about i would check with the A.H.J. On this

Cass
10-28-2008, 03:44 AM
I would absolutly put an expansion tank in. The code never asks for my opinion or how I feel about things. The words "shall" hold up in a court of law. Do I agree with putting a tank in? No, but because I am constantly worried about laibility (and so should you all be) I do everything to code. Then there's no questions, no arguments, no liability.

HJ there is a foot valve at the bottom of the well drop if it's a shallow well pump and a check valve on top of a submersible pump.

So the bladder tank is not an expansion tank...

Ladiesman271
10-28-2008, 05:14 AM
Hey N.H. Master i usually agree with what you are posting,
but i think on this one you had better go back and reread
the mfg's instructions about installing tank on cold side
because in all my experience reading install directions and water
heater mfg's install diagrams the expansion tank goes on the cold side between the shut off valve and the water heater




Instructions? Trained professionals in NH don't need to read no stinkin instructions!


Is there a liability issue for not following the manufacturers written instructions?

Cass
10-28-2008, 05:17 AM
In the same vain. There was discussion about whether or not the tank could go in the cold side. Since the manufacturers instructions say to install in the hot side, putting it in the cold side would be a code violation because the code says to follow the manufacturers directions if there is no specific code entry.

I don't know what planet your from but maybe they don't read there...

http://www.watts.com/pro/divisions/watersafety_flowcontrol/learnabout/learnabout_thermexpansion.asp

nhmaster
10-28-2008, 06:01 AM
Woops, sometimes at my advanced age I get confused. Cold side yes. Hot side no. Sorry for the confusion. Ahhhhh. no, technically the water tank can not be substituted for an expansion tank. Again the code does not say you can substitute it that way. However, I do agree that it should be allowed. Sometimes things slip through the code.

how about this nasty little blurb in the IPC that says you have to use city water if it's available. Even if you have a perfectly good well on your property.