How often is normal for a pressure relief valve to discharge?

[Lvrpl]

I recently got a new water heater installed (a 75 gallon AO Smith powervent), about two months ago. In the last 3 or so weeks, I've noticed that the pressure relief valve has discharged a few times - maybe 3 or 4 times. Each discharge is maybe a couple of pints of water, I'd guess.

Is this normal? My previous heater, a 20-year-old Lochnivar, never discharged during the 5 or so years that I've owned the house.

Thanks for any help.

 

[Breplum]

NOT normal unless your home has pressure above 80 psi. If it does, then there can be factors like a water pressure reducing valve that does not have 'bypass' built in, and in that case you need an expansion tank.

 

[Sponsor]

 

[Fitter30]

Standard wh relief valves either open at 150lbs and or 210°f. Expansion tank needs to be checked if one isn't piped into system it needs one.

 

[Lvrpl]

Ok thanks for the help. Is it problematic if I can't get someone here to address this for a couple of weeks? Or is this much more urgent?

 

[Fitter30]

What changed when tank was installed. Size or pressure reducing valve?

 

[Tuttles Revenge]

Ok thanks for the help. Is it problematic if I can't get someone here to address this for a couple of weeks? Or is this much more urgent?

Waiting 2 weeks should be fine. But I would have the relief valve replaced as it could be defectively weak.

As Fitter asked.. Was there any changes to the installation? Was there an expansion tank previously that wasn't installed now? Or was the pressure not accurately set on a new expansion tank to match static pressure? Or was or is there a Pressure Reducing Valve that has failed or not in place? All of the above can affect the water pressure when the water heater fires up and the cold water molecules expand.. that expansion needs some place to go.. and currently its out the pressure relief valve.

 

[Jeff H Young]

Another possibilty is a defective or malfuntion of the TandP valve? Am I the only one who has replaced TandP on a new or even newish water heater? Its very common to have nothing else wrong, but also very common to have an illegally closed system with either a bad x tank or none at all
Its only urgent if the spilling of water bothers you

 

[Lvrpl]

Thanks for all the help so far.

The new heater is the same size as the old heater - 75 gallons. The old heater didn't have an expansion tank. I suppose the old heater could have had a pressure reducing valve that the service tech didn't replicate, but I don't think so. I think the setup now is the same as before, although I can't say that 100%.

I suppose the most likely culprit, given that I don't believe anything changed on the setup, is the t&p valve?

 

[Jeff H Young]

Like I said it might be the t and p try releasing pressure several times it might clear debris