Water Heaters - Pressure Relief

I just replaced our 50 gallon electric heater with the same model we had previously. The past two nights, I've had a lot of water (about 3 gallons) coming from the pressure relief valve. This never happened with the other heater, and it only happens at night. I've read about expansion tanks, but wonder why I would need one now when I haven't before. Thoughts?

Welcome to the forums!

Have you checked your water pressure lately? Pressures tend to increase at night. Your pressure regulator may have gone bad.

Thank you! No I haven't checked the pressure lately. How do I do so and what should I look for? If the pressure is to high, can I assume its the regulator? If so, is replacement something a moderately skilled homeowner could tackle, or is it a job for a pro?

To accurately test the water pressure, you need a gauge. I bought mine at lowes - under $10 if I remember correctly. You just screw it on a hose bib and it will tell you the pressure, leave it connected for a while and when you come back it will indicate what the highest pressure was.

Replacing the pressure regulator isn't all that hard [I'm a painter and hate doing plumbing work :D] you will need to shut off the meter, trip the breaker for the water heater and allow for the pipes to drain [unless there is a cut off just bast the regulator] Last one I bought was close to $30

thanks again for your input. I bought a gauge, and placed it on the water spicket outside. when I turned the water on, the gauge pegged at above 200 psi. that can't be right (without blowing all my plumbing), can it? now that I've taken it off the spicket, the needle is stuck at about 60 psi--is that the correct reading? I seem to have had this experience with a pressure gauge before. am I using it incorrectly?

I'm afraid that you destroyed the gauge. Sometimes outside hose spigots are piped ahead of the house water pressure regulator. That is why I always recommend connecting the gauge to a laundry hose connection.

Still, you should not have en excess of 200 psi even coming close to your house. I think a call to your local water utility is in order. And, if you had 200 psi getting past your home's pressure regulator it would be constantly blowing through the T&P valve on the water heater as these are set at 150 psi maximum pressure.

the pressure regulator is actually the first thing into my house--before the hose spicket. if it were truly 200 psi, wouldn't there be other noticeable problems (leaks, faucets blowing, etc)?

like you said, it would also be blowing the T&P valve constantly, whereas its only happening overnight.

am I reading the gauge correctly?

When you peg a meter like that, it may be damaged beyond help. Check to see if the hose bibb you are connecting to is ahead of the PRV.....that is often the case on a front bibb.

Frankly, 200 PSI is a lot for the city to be providing to you. And yes, at 200 bad things would be happening in the house.