Yet another water heater PRV question…

[Bald Point]

Hopefully I won’t be too redundant here.
I have a gas Rheem water heater that is relatively new (less than 5 years old) and went for several of those years trouble free.

Recenetly, if it is turned above the “Warm” setting (which is not really hot enough for some residents’ showers) it begins spewing water constantly from the PRV and causing a groaning in the pipes that can be heard everywhere in the house. Needless to say, we’re losing a lot of heated water this way.

What has me baffled is that it went for several years with no problems and all of a sudden this… Could the PRV need replacing? I have opened if fully and closed it repeatedly many times to try and loosen any sediment, etc. to no avail.

Thanks in advance for your help and your patience for yet another PRV question!

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Cheers,
Chuck

[Retired plbg1Participant]

Go two lines up from your message and that guy has a good solution for you.

[cgh1Participant]

Hey Retired Plbg,
Thanks for your reply. I’m not sure how you have your items sorted/displayed. Two items up from mine is someone with a question about central heating and radiators, and I can’t see how that applies.

If I go two items down, there’s a discussion on how to connect multiple water heaters to get larger capacity. Again, not sure how that applies to my problem. Plus that sounds about $400 too expensive for my budget.

Could you be a little more specific or give me the subject line text for the item to which you refer?

Thanks!

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Cheers,
Chuck

[SelgasParticipant]

Ok you lot it’s my turn to try and assist this fellow so here we go.
Firstly the valve you are referring to is called a TPR valve (temperature and pressure relief) it is designed so that is the water rose to a temperature greater than 99 degrees C, or the water pressure exceeded the valves rated specifications then it will open and discharge or release the pressure via the valve to waste.
However, with over 35 years experience with gas fired water heaters it is commonplace for this to happen on ocassion due to the extreemly rapid heat up capability of the gas burner used in the water heater.
To overcome this problem install a pressure limiting valve on the inlet to the cylinder and a cold water releif valve on the same line rated at 70% of the maximum setting of the hot water relief valve. This will allow the expansion to discharge cold water when the main burner is firing and keep your gas operating costs to a minimum.
Hope this helps.

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Selgas Services Ltd
Craftsman Gasfitters, Plumbers, Electrical Service Technicians

[Retired plbg1Participant]

Thats the post I was talking about, The one from Peter.

[cgh1Participant]

Got it – thanks!

Here’s the part that stumps me:
The unit just decided to start this behavior one day after a year or so of working perfectly. Once the temp dial is turned to the “normal” position (120 degrees F according to the manual) it then begins the problem. The groaning and leaking that is. Once it starts the problem, it does it continuously (as in non-stop) whether the burners are actively on or not. I suppose the water gets overheated and stays that way forever. It seems as though using the water would cool it down some and stop the TPR leakage. Doesn’t it seem as though it would have done this from the beginning unless something went wrong? I guess that’s why I’m not a plumber, and you guy make the big bucks

I suppose my next logical step would be to measure the temp of the water coming out of the tap and the TPR valve. Perhaps the temp dial on the unit is no longer accurate.

Thanks!

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Cheers,
Chuck

[SelgasParticipant]

Nope that is NOT the answer – read my post and follow the instructions therein and you will not have anymore problems – it should have been installed the way I have said from the get go.

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Selgas Services Ltd
Craftsman Gasfitters, Plumbers, Electrical Service Technicians

[cgh1Participant]

Thanks a million guys!

Peter, will hooking up the second relief valve allow continued water spillage? I assume that is the reason for the pressure limiting valve.?

Right now, when it does this, the flow of water from the TPR valve is continuous (and the loud groaning noise maddening), not just when the burners are fired – leading to extremely high water bills and a constantly wet basement floor. The drain is in the middle of the floor in the area where the WH is located so a pipe run all the way to the drain becomes a trip hazard.

You guys are awesome!
Thanks again!!!

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Cheers,
Chuck

[SelgasParticipant]

1. The purpose of the limiting valve is to ensure that the cylinder is not subjected to excessive cold water inlet pressure which can affect the operation of the TPR valve.
2. The purpose of the cold water relief valve is to ensure that should the pressure applied within the system exceed the valve setting it will discharge colder water thus saving you energy in running costs.
3. Fit the pressure limiting valve first if this does not stop the hot water relief valve from continually discharging you will have to replace the HW TPR valve as well.
4. Fitting a cold water relief is a manufacturers recommendation and is not compulsary, however I would strongly recommend you do in fact fit one – remember to get on rated at 70% of that of the hot water relief valve.

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Selgas Services Ltd
Craftsman Gasfitters, Plumbers, Electrical Service Technicians

[cgh1Participant]

Excellent.
Thanks again for all your help!

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Cheers,
Chuck

[Author]

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