Hot water expansion tank

Mikebarone · Feb 4, 2008

I have a client that has a home that has two electric hot water tanks. One tank does one half of the house, and the other tank does the other half of the house. Recently, she had a plumber install a pressure reducing valve on her house and, (because of what Iâ€™ve learned on this great forum) she now has a closed system and she needs an expansion tank. The PRV is set at 60 psi. My question is, do I need to install two expansion tanks, (one for each hot water tank) or could she get away with just one tank on the incoming cold water line, (after the PRV) like by her water softener?

Thanks all,

Mike

Gary Swart · Feb 4, 2008

One tank would be sufficient, but I would opt for the larger size. Install it between the PRV and the first water heater.

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Mikebarone · Feb 4, 2008

Thanks

Gary Swart said:
One tank would be sufficient, but I would opt for the larger size. Install it between the PRV and the first water heater.

Thanks Gary. The Home depot by my house only sells one size, (ie one tank for one hot water tank). I will get on the web site that makes the tank, and see if I can get the next size.

Thnaks again,

Mike

Construct30 · Feb 4, 2008

I would just watch the price with shipping, it might be cheaper to go with the two expansion tanks. Also size does matter so be sure you get them to size it if you order one.

Jadnashua · Feb 4, 2008

I think it is Watts that has an expansion tank size calculator on their website. You enter the size of the WH(s), the expected temperature rise, and it tells you what size tank you need. They usually come precharged with 40# in them, if your PRV is set to 60, you'll need to add some air to it.

MACPLUMB · Feb 4, 2008

Hot Water Tank

You need two expansion tanks, one on each water heater,
BETWEEN THE COLD SHUT OFF ON EACH HEATER ! ! !
otherwise the tank can be isolated by any shut off's in system,
and still pressure bulge or blow up without expansion protection

JERRYMAC MASTERPLUMBER
PH.D WATER HEATEROLGY ! !

Redwood · Feb 4, 2008

Our resident PH.D Waterheaterologist is correct! I was scrolling down to post the same thing when I saw his post.

Gary Swart · Feb 4, 2008

Thank you for that information Dr. Jerry Mac. I stand corrected.

Mikebarone · Feb 4, 2008

All good points...thanks!!!

As usual, I want to thank everyone for all of the great inputs. I tell everyone how great this forum is. You all make this handyman look somewhat intelligentâ€¦.LOL!
This poor ladyâ€™s house was build by her ex-husband, and you wouldnâ€™t believe some of the, â€œshort cutsâ€ Iâ€™ve found in the past three years Iâ€™ve been working for her. The first day I went to work for her, I was just going to replace a bad started switch on her outside stainless steel BBQ. After I noticed that the back of the switch was melted, (and I found that three of the six gas valves were leaking), she had me there for a total of 12 hours that day fixing other thingsâ€¦LOLâ€¦and Iâ€™m not done yet!

Thanks all again,

Mike

Cass · Feb 5, 2008

According to the Watts info here

http://www.watts.com/pdf/ES-PLT.pdf

The Watts PLT-12 (large tank) will handel up to 120 gallons being heated / expanded at a water pressure of 60 PSI.

2 expansion tanks is a good idea but not necessary, I have been in very few homes that have a valve between the main and the water heater or heaters valve.

hj · Feb 6, 2008

heater

otherwise the tank can be isolated by any shut off's in system,
and still pressure bulge or blow up without expansion protection

If that did happen then she also had a defective, nonfunctional temperature/pressure relief valve, AND if so, and conditions were such that a blow up could occur, all the expansion tanks in the world would not prevent it.

MACPLUMB · Feb 6, 2008

Hot Water Tank

It's called murphys law ! !

it should be installed between cold shut off and tank,

if do'es not have this protection voids MFG'S warrenty on leaking tanks

JERRYMAC MACPLUMB 777

Mikebarone · Feb 7, 2008

MACPLUMB 777 said:
It's called murphys law ! !

it should be installed between cold shut off and tank,

if do'es not have this protection voids MFG'S warrenty on leaking tanks

JERRYMAC MACPLUMB 777

Good point!!!

Thanks, Mike

Hot water expansion tank

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