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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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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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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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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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