Water Pressure Spiking- Blowing PRV

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Funkytown

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A couple of years ago, we replaced the pressure release valve on our hot water heater because it kept blowing. That didn’t help, so we replaced the hot water heater. Since then, nothing has really changed except that we found out that we have a pressure regulator, so we replaced the pressure relief valve and adjusted the regulator to about 60psi. However, it keeps getting spikes and hitting 140 (instead of 150 prior to regulating the pressure). My question is that if the regulator is keeping it at 60 psi, is it functioning properly? Or, since it’s still spiking, that it’s not functioning properly? I don’t know if it’s supposed to simply keep it at a certain psi, or if it should also not allow it to spike?



The pressure regulator valve was here 23 years ago when we moved in.



Thank you for the help!
 

GReynolds929

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So is the problem that the water heater T&P is popping off? Or the PRV is not regulating pressure? If it happens when the water heater heats water, then it's thermal expansion. There should be a thermal expansion tank that probably has waterlogged or failed. If there isn't one you need to install one.
 

Jeff H Young

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23 year old water pressure regulators are always bad I check em and they need replacing but lets just say it needs checking , secondly you might need a thermal expansion tank.
 

Reach4

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"adjusted the regulator to about 60psi."

On your new thermal expansion tank, set the air precharge to 60 or 61 psi. Those are usually shipped with an air precharge of 40 psi.

Air precharge is set while the water pressure is zero.

You can take the new tank to the tire store to add air before installing.
 

Funkytown

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So is the problem that the water heater T&P is popping off? Or the PRV is not regulating pressure? If it happens when the water heater heats water, then it's thermal expansion. There should be a thermal expansion tank that probably has waterlogged or failed. If there isn't one you need to install one.
Sorry, it was showing this post as pending approval and didn't see replies. The T&P squirts water several times a day. Sometimes it goes days without anything. The PRV I have regulated down to around 60, but there will be something that happens and I'll get a spike up to 140+ but remain around 60 at other times.

Also, I do not have a thermal expansion tank
 

Funkytown

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23 year old water pressure regulators are always bad I check em and they need replacing but lets just say it needs checking , secondly you might need a thermal expansion tank.

Should I replace that and then see how it goes or should I do both at the same time?
 

Funkytown

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Should I replace that and then see how it goes or should I do both at the same time? Seems like something is causing it to spike. An expansion tank might be able to handle that and I can continue to use my current regulator. Would prefer not to replace both if I don't have to.
 

Funkytown

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Should a regulator even allow the spikes? I'm unfamiliar and didn't know if if that's not really it's purpose
 

Valveman

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Thermal expansion from the water heater can cause higher pressure than what is coming in. Regulator can't do anything about thermal expansion unless it has a thermal bypass built in. Yes you need an expansion tank.
 

Jeff H Young

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Test regulator, since you are experiancing problems you really need a guage unless you have a plumber you trust and dont mind paying him to unravel the situation . I recomend the purchase of a test guage . I exagerated a bit but really 23 years is beyond life of id say every regulator ive checked perhaps a few were still good or rebuilt i dont check ages.
BTW the regulators that Ive read instructions on Ive never seen a thermal bypass but a pressure bypass that allows pressure to go back towards the main if pressure gets above the high pressure on upstream side
 

John Gayewski

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The regulator is either not shutting completely or the expansion tank is not set up correctly or the expansion tank is too small or you've already broke your expansion tank.
 

GReynolds929

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Regulator is failed if it let's in higher pressure than 75psi. If not failed it seems clogged. Definitely need thermal expansion tank.
 
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