I have a maytag h/w heater. In the last few months it has started releasing water via the TPR after it reheats (from a shower or something). Never has happened before, nor did it happen with the other 2 water heaters I have had in my home over the last 30+ years. Water company (I live in St. Louis) says they have not done anything with the water pressure... and while I do have a pressure control valve, it is also reasonably new - I replaced it some years ago (slightly before the new w/h actually).

General water pressure is fine. No problem with getting enough hot water... everything seems to work great save for the TPR release.

While I am okay putting on a thermal expansion unit, given that this has never previously happened, and nothing I can tell has changed, I am concerned that actually there is something else going on... is there anyting internal to the water heater that could be bulding up and causing this? I haven't replaced the TPR... but that seems like a long shot given it only releases water after the heating cycle...

Any idea?

Is the water hotter than normal? This could cause the issue if one of the thermostats is malfuntioning. However, I would start by merely replacing the t/p valve as they do now and then go bad. That is a good cheap/easy place to start. If the problem persist, we will look further into the problem. I would say over fifty percent of the leaking t and p valves that I come across is simply a bad valve. Good luck and please let us know how things turn out.

That valve should only release under 3 conditions; temp above 210, pressure above 150psi, when broken. You have one of those 3 conditions. I'd connect a pressure valve to the drain spigot to see if it psi first

Thanks... I will do the PSI test and if okay replace the TPR... and let you know. However if the PSI is higher... my question would change to what cause the PSI to change all of sudden? (As you can see I am unexplained change averse!).

Some homes need an expansion tank to absorb the pressure caused when cool water is heated and expanded in the water heater.

Some homes have a PRESSURE REGULATING VALVE... if that valve fails then you would see a rise in pressure and water might drip from the T&P valve during the water heating cycle.

In this case an expansion tank will not help the issue, but instead, replacing the pressure reducing valve will... ;)

Check the pressure and let us know what you find, OK?

Mark

I do have a pressure relief valve - always have. Replaced it several years ago due to abysmally low water pressure - that has been great ever since. It sits above a finished ceiling (with access panel) and there is no water marking, so I don't think it is failing per-se... at least not in the sense of leaking...

I did put a pressure gauge on the drain valve - it ran up to 150psi and the TPR started letting water out... it is slowly going back down since the burners have kicked off... so I am sure that meant the TPR is good.

One other strangeness about my water heater that happens (and I thought was unrelated) is that the beginning about 2 years ago the burners would kick off now and then with no pilot light left. Maytag said that was due to dirt/dust build up in the air intake chamber / filter. Since the h/w heater is next to my workshop, it was feasible I was getting more dust than normal (again, however this did not happen the previous 2 years for this w/h). Ever since then - and somewhat consistent with when I work (and especially sand) in my workshop, I have the problem with the burners going out before fully heating the water. And while there is an obvious connection, quite honestly the amount of dust is not that bad and I have had it turn off even when I haven't worked near it for a few weeks. I am now thinking that the temp shut off is somehow not working right - too sensitive to dust or (now that I have confirmed that the TPR is okay, and nothing has changed with my overall "closed" system) allows the water to heat higher than expected - thereby creating the pressure that causes the release. I keep the temp gauge between A and B and it doesn't seem to all that much hotter (although I have to admit I have not tested right after the tank fully reheats). So my next cheap fix is to turn down the temp setting to less than A and see what happens.

sorry for the long post if you are still reading... but wanted to fill in on all the variables at this point.

Pressure relief valve sits on the top side of your water heater. I think you mean a pressure reducing valve. If your psi is 150 then that valve needs to be adk=justed or replace. Most of us shoot for around 45 psi

Sorry I wasn't very clear. I do have a Pressure reducing valve (just past the main shut off valve in my basement). I tested the pressure at the drain valve on the water heater - that went to 150psi and the TPR started releasing water. After/since the water heater burners turned off, the Pressure has since fallen to 50 psi (as measure on the water heater drain valve). I also measured the pressure at the faucet for the washing machine and it too registered 50psi.

Should the water heater stay at 50psi while heating? Or does the pressure increase but should not go above 150PSI?

I am sorry I have just realized I have been confusing the pressure relief value - I have been calling it a TPR... what I was thinking about in terms of what I calle dthe pressure relief valve was the pressure regulating valve.. that seems to be good..

I probably have everyone confused... including me... so..

If my pressure relief valve on the side of the water heater starts letting water out at 150psi then that seems like it is working as expected.

However it does seem that 50psi the normal pressure within my plumbing system, and the water heater returns to that once the burners have heated the water.

So I still not sure if the pressure in the water heater is expected to go up during the heating cycle or stay at 50psi...

am sorry I have just realized I have been confusing the pressure relief value - I have been calling it a TPR... what I was thinking about in terms of what I calle dthe pressure relief valve was the pressure regulating valve.. that seems to be good..

I probably have everyone confused... including me... so..

If my pressure relief valve on the side of the water heater starts letting water out at 150psi then that seems like it is working as expected.

However it does seem that 50psi the normal pressure within my plumbing system, and the water heater returns to that once the burners have heated the water.

So I still not sure if the pressure in the water heater is expected to go up during the heating cycle or stay at 50psi...

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I did put a pressure gauge on the drain valve - it ran up to 150psi and the TPR started letting water out... it is slowly going back down since the burners have kicked off... so I am sure that meant the TPR is good.

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If your House PSI spikes at 150 then you have almost double the pressure that you should have. I think installing a expansion tank.(see image) would absorb the spike and keep a normal pressure in your house. Good luck, Tom

Jim, what is your psi normally when the plumbing system is at rest? You mentioned 150 psi which is huge. I do not think your pressure runs up from 45 psi to 150 psi just from the water heater heating and expanding the water. The pressure REDUCING valve on your main is adjustable and needs to be tightened to drop the normal at rest psi to 45 psi. I think your "spike" will no longer be 150 and all will be fine. BTW, a failing pressure REDUCING valve has no outward sign, you can't see the failure by looking at the valve.

The PSI of my plumbing system while at rest is 50psi (might be tad lower its an analog gauge, but I do have a vague memory of when I bought it the guy told me it was set for 50and that was what St. Louis required). What I have not yet tested is whether the PSI of everything else in the system spikes to 150 while the water heater is actually heating the water (based on the comments I would presume it does). When I put the PSI gauge on the water heater drain, I thought it was only measuring the pressure in the water heater... not the full plumbing system.

If my pressure regulating valve was bad would it hold the 50 at rest, but should it be doing something else to relieve the build up of pressure when the water heater is heating? Is the pressure regulating valve going bad why I would start getting discharges from the pressure relief valve after 4 years?

"only measuring the pressure in the water heater ... not the full plumbing system." Nope , that measures the whole system not just the heater. Why the discharge after 4 yars, well, maybe that's how long it took to start failing. So now lets go back and put the gauge on the drain. Open the spigot and allow some COLD water to run from a faicet elsewher in the house, wait a few minutes, what is the gauge reading?

Bob,
Sure sounds like the pressure spike's coming from the water heater and that leaves the PRV out of the loop. I don't know why the heater spikes to 150 PSI when the burner kicks on but I place the problem squarely on the heater itself. Before anything's done he should have the heater checked out by a professional. Your thoughts Cheers, Tom

I did a few tests.

For the one you suggested - the meter read 48ish (it seems to vary a bit). Ran a cold water faucet and it sank to 40. Turned off the faucet popped back up to 48.

Second test was to flush a toilet... sank to 20-something, and then built back to 48ish.

A third test I just did was to turn the water heater to pilot only, ran the hot water out of a faucet for about 5 minutes, left the PSI meter on the cold water washing machine faucet, and then turned the water heater dial back to on. Burners kicked on, and eventually the PSI reading slightly above 60 when the burners kicked off (no discharge from the pressure relief valve). I think this just confirms what you all have been saying - the pressure reading is for the whole system regardless of where I take the reading. But the nut of this test is that if the heater does not run too long, I don't get the drastic pressure build up.

And just for clarity... last night when I was getting the 150PSI reading... the water heater pilot had gone out (a separate and occasionally recurring problem), I (unknowingly) took a (rather luke warm) shower, and then re-ignited the water heater pilot and burners. It heated the water for a good long time (20 minutes maybe)... so obviously the longer it heats the greater the pressure it generates until it gets the water to the temp setting (between A and B - again what it has always been set at).

Is the pressure regulating valve supposed to release something when the internal system gets to higher pressure? (I thought the whole purpose of the pressure regulating valve was to prevent my system pushing something back into the main water supply system, and hence ought not "relieve" any internal build up of pressure by letting water back out. )

Hi Jim

At this point, it seems to me that we have an issue with pressure only when heating the water up for awhile, but whether the spike occurs over long or even short heating cycle you are getting build up of pressure and no place for it to go.

To me, this suggests that something has changed in the plumbing system, such as a check valve being installed... the new PRV in itself is a check valve(;)), a backflow preventer, or maybe you had a sprinkler system installed and they changed some of the plumbing around... maybe? Any one of these could be the issue!

Whatever it is, it sounds like you need the expansion tank at this point... should resolve the issue for you. Of course, it would be nice to know exactly what changed here, but if you can't determine it at this point, I'd install the expansion tank... not an expensive job!

Good luck!

Mark

PS: The PRV does NOT release anything when excessive pressure is present (unless you have a combo. PRV and pressure relief valve, which I doubt!). Any "release" as a result of excess pressure is spilled from the T&P valve just like your valve is doing!

Mark - thanks. If something change it has completely escaped me. However it seems an expansion tank is the next less-expensive step... and probably not a bad thing even if it doesn't help this problem and it's the water heater itself that is the problem.

Does it matter if the expansion tank is put on the cold water line before or after my shut off valve going into the water heater? I presume not...

I plan to do the expansion tank install this weekend to see if that fixes my problem. Once installed what should be max PSI that I should see during the heating cycle... should it ever go much over the 45-50 PSI that I am registering at rest?

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Does it matter if the expansion tank is put on the cold water line before or after my shut off valve going into the water heater? I presume not

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You presume wrong! Look at the image I've put up. The expansion tank installs After the heater shut off valve,

[QUOTE I tested the pressure at the drain valve on the water heater - that went to 150psi

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Twice the PSI your house should have, [QUOTEwhat should be max PSI that I should see during the heating cycle... should it ever go much over the 45-50 PSI that I am registering at rest?]

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That you'll have to check for yourself. The water will expand as it heats but the tank should absorb The spike.
A few questions, b What's the house PSI at the present time? When the heater fires up is there any noise? Let me know, Tom