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I just installed a new water pressure regulator as documented in Water Pressure Regulator not regulating after rebuild.

I left the pressure gauge attached to a hose bib with the faucet turned on so I could monitor the pressure over the course of a cpl days. My gauge has a red, maximum pressure, hand to record the highest measured pressure during that measurement period.

So far everything is working as expected, and it's able to control the pressure to 60psi where I set it, except sometimes when I leave and come back several hours later, I see the maximum pressure hand read high over the 60psi.

Once it was up at 80psi, the other time it was at 110psi (from other tests I've done, I assume 110psi is the city water pressure level, and this is the same pressure I was reading on the old regulator that went bad before I replaced it).

From reading other articles on the site, I understand one possible cause is the water heater heat cycle expanding the water and increasing the pressure in the system, although I'm not sure about this.

I don't see an expansion tank on my water heater, and I don't think there's any pressure release valve anywhere in my house water line.

Any ideas what the issue could be, and how I can solve it?

Update Pics of my TPR.

And it looks like where it connects to the wall is leaking. Any idea how to fix that leak. Is that solder?

SDSHuge2.0
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  • The answer is in your question. Self answering is acceptable here, so put the 5th & 6th paragraphs in an answer box along with the thing you need to add that they imply. Though if you can stand a little while without much hot water, you could turn the water heater off to verify (you'll still have the hot in the tank, until it runs out.) – Ecnerwal Feb 21 '23 at 13:30
  • There should be a pressure release valve on the hot water tank. Other thing to check is the thermostat on the hot water tank(~ temp setting around 130/140F). – crip659 Feb 21 '23 at 13:37
  • @crip659 Your suggested temp setting is a little high, 120-125 would be safer. – George Anderson Feb 21 '23 at 17:40
  • @GeorgeAnderson There seems to be a debate about the right temperature now. 120 is right for not burning people, but might be too cool to stop nasties growing in the tank. Those new flangle anti-scald devices should keep both camps happy. – crip659 Feb 21 '23 at 17:47
  • @crip659 I've been running mine at 120 for years and years without a problem. If the OP wants to run it hotter, a mixing valve at the WH could be used to temper it down to a safe temp. – George Anderson Feb 21 '23 at 18:26
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    You can find solid defense for nearly any temperature between 120 and 140. Wandering in to that debate is likely not what OP wants! And @Ecnerwal is spot on, turning the tank off is the super quick diagnosis path. – KMJ Feb 21 '23 at 20:00
  • Thank you to everyone for your replies and suggestions. @crip659 I found the water heater pressure release valve on my water heater, but the YouTube video I watched said they trigger at 150psi and/or 210 degrees F. I think I need something to address the pressure before it gets to that point, because I'm trying to relieve pressure increase in the water line. I did test the release valve, though, and it seemed to be stuck on my first attemp. Had to use a little force to release it, but after that first one, it's openning smoothly now. – SDSHuge2.0 Mar 04 '23 at 12:08
  • To the comments about water temperature, I didn't see any thermostat to check the temp, but the dial is set to 'Hot' out of options Low, Hot, A, B, C, Very Hot – SDSHuge2.0 Mar 04 '23 at 12:08
  • @Ecnerwal my comment about no expansion tank or pressure release valve were meant as observation as opposed to suggested solution. I really don't k ow what's needed. Great idea to try shutoff the water heater, but it's tough to shut it off because I live w/3 other roomates all on different schedules, but I think that might not be necessary because of another observation that I'll explain in my next comment. – SDSHuge2.0 Mar 04 '23 at 12:08
  • I forced the water heater into heat mode by letting the hot water run on the sink faucet. While the heater was heating, I observed the water pressure steady rising over the 60psi thst I set the regulator to into the 80's (maybe higher. I opened the faucet to relieve the pressure after I saw it go to 80) So is that pretty certain that I need to install an expansion tank, or should I opt for a pressure release valve in the water line? – SDSHuge2.0 Mar 04 '23 at 12:15
  • The pressure release valve on the tank is for safety only, not regulation of the pressure. It keeps the tank from turning into a bomb. – crip659 Mar 04 '23 at 12:20
  • Got it, thanks! Unfortunately, when I activated the TPR valve, it got stuck and wouldn't close completely even after I've tried openning/closing it several times, and unfortunately it's solder/flashed (dunno really what it is called). So now I have to figure out how to remove those so I can replace it – SDSHuge2.0 Mar 06 '23 at 21:51

3 Answers3

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Sounds like water hammer causing very brief pressure spikes as water flow is shut off abruptly to something (ice maker, washer, dishwasher, etc.)

user163347
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    If it still happens with the water heater turned off, might be this sort of thing. But I'd bet on the missing expansion tank. – Ecnerwal Feb 21 '23 at 17:20
  • Hi, thanks for the suggestion. If you read the Answer I just posted, I can confirm that flushing master bedroom toilet causes pressure spike up to 110psi... suggestion? Should I start a new query for that? – SDSHuge2.0 Mar 06 '23 at 21:50
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Presumably your water heater already has the standard temperature/pressure release valve installed (which will typically be set at 120-150 PSI for pressure) so what you need is an expansion tank - that goes anywhere on the cold water supply between the PRV and the water heater.

Or anywhere it's convenient on the cold water supply after the PRV, really - if you don't have any oddball check valves that would not be typical, the entire cold supply is connected, so the expansion tank will work anywhere on it.

Ecnerwal
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  • Thank you so much! That's the conclusion I just came to myself, but I really appreciate the confirmation also. I just checked the pressure guage again just now, and the red hand showed it had been up to 100psi at some point. What I don't understand is if all residential water systems will suffer from high water pressure over where the regulator valve is set, then why isn't an expansion tank a standard installation? Doesn't that mean people are damaging their waterlines and appliances without one? – SDSHuge2.0 Mar 04 '23 at 13:42
  • It's not all systems. Not everyone has a PRV or check-valve, so in many cases excess pressure went right back out the water meter. I have a well system, which has a pressure tank which is basically a much larger expansion tank, so I don't need one. They have been added to code requirements recently due to the proliferation of PRVs and water meters with check valves built in, but systems that predate those updates to code won't commonly have them. You are unlikely to "damage your pipes" below the point where the water heater's TPR valve will let go. Toilet fill valves tend to be the weak point. – Ecnerwal Mar 04 '23 at 14:00
  • I see. That makes sense. Thanks very much for the explanation. – SDSHuge2.0 Mar 04 '23 at 14:02
  • If you want to edit in pictures of your water heater we can point you at the TPR valve - it's highly unlikely not to have one. Usually either on top, or on the side near the top. – Ecnerwal Mar 04 '23 at 14:11
  • Thank you! I found the TPR valve. It was stuck closed. I had to use a little force to open it the first time, but it opens smoothly after that. But I understand that the TPR releases at about 150psi, and I though it's reccommended to set the PRV mo higher than 80psi to protect appliances and pipes, no? – SDSHuge2.0 Mar 04 '23 at 14:16
  • Yes - the TPR is purely for safety, not for regular use. If it opens, something is seriously wrong. If you have your PRV set for 60 PSI, you set your expansion tank bladder to 60 PSI (**before** installing it, or with no pressure on the water side) and it gives compliance for the expansion as the water heats. – Ecnerwal Mar 04 '23 at 14:21
  • Got it! Yea, so I think I'll put in the expansion tank. I just editted in pics of where the TPR flows through the wall and out side, and it seems like that join pictured is leaking. I the the wall side pipe is copper (hard to tell cause it's painted), not sure what the heater side pipe is. Any ideas how to fix the leak or join them together more securely? Solder? – SDSHuge2.0 Mar 04 '23 at 14:25
  • Should not be a big deal, since water should not regularly flow in it. Yes, it's copper pipe, some of which has been painted, you'd have to remove the paint, get it apart, and re-solder it ofter cleaning up the inside and outside of the joint. But since it should literally never flow outside of the emergency failure mode, a minor leak should not be an issue, until it's time to replace the water heater. – Ecnerwal Mar 04 '23 at 15:04
  • Thank you very much. I was literally just thinking the exact same thing that it's probably fine to leave the leak since it really should not trigger in normal operation anyways. Earlier you said "You are unlikely to "damage your pipes" below the point where the water heater's TPR valve will let go." So does that mean the expansion tanknis 'optional' even if my pressure is getting up to 100-110psi? – SDSHuge2.0 Mar 04 '23 at 15:27
  • Pipes will stand more. Things like toilet valves may not. I would not consider it optional for the situation you describe. – Ecnerwal Mar 04 '23 at 15:36
  • I'm going for it! I'll post my results when I get done. Thank you again very much! – SDSHuge2.0 Mar 04 '23 at 15:43
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Thanks for everyone's suggestions and guidance!

I forced my water heater into heat mode by increasing the temp to the max setting, and I confirmed that in fact the water heater was in fact causing the water pressure to rise

I watched this YouTube video as the blueprint for my installation: Expansion Tank Installation on a water heater - What is an expansion tank? - How to install it

Before/After: enter image description here enter image description here

After installation, I no longer observe the temperature rising due to water heater heating.

One thing that I did when I was refilling the water heater w/water after installing the expansion tank was to leave the TPR open to let air escape. My logic was that I didn't want trapped air to put pressure on the expansion tank diaphragm and reducing the efficacy for the actual purpose of absorbing the pressure of the expanding water. Not sure this was necessary, though. But I did it.

I also detected that flushing master bedroom toilet spikes the water pressure up to 110psi.

BMitch
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SDSHuge2.0
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