Discharging T& p valve.

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TheGreatSeagull

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So I have a new hot water heater just installed a few days ago. On the day of installation, the T&P valve was leaking. We replaced the valve with a new part from the building supply store. The water temperature is set at 140. The T&P valve discharges a small amount of water when the tank refills after a shower. The guy at the support line tells me that there might be an issue with the pressure coming in to my house. I'm on town water, and never had an issue with the previous hot water heater discharging, but it was leaking(from somewhere else) before we replaced it. He told me I need a "dead head gauge" to check it. I guess I'm looking for help on two fronts? Can I get some information about the gauges, and do I need a thermo expansion tank. My brother in law installed the water heater, but isn't familiar with the expansion tanks. Thanks in advance.
 

Twowaxhack

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Get one of these

Screw it onto the water heater drain valve and open the drain valve.

Read the pressure. It should be 80 psi or less.

Next step:

Leave gauge in place.

Run enough hot water to make the water heaters burner fire up. Roughly 10-15 gallons would be good.

Make sure no water is being used, no drips.

Watch the gauge as the water heater heats. It should NOT start rising in pressure.

If it does, that’s thermal expansion and it must be controlled. The most popular way is installing a properly sized thermal expansion tank and it charged to the correct air pressure.

It sounds like you’re experiencing thermal expansion to me......
 

havasu

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You owe it to the folks inside that residence to check the incoming water pressure as soon as possible.
 

arctic bill

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if you have a check valve on the incoming water like then this would cause this type of condition,
You will need a water heater expansion tank not heating expansion tank , there is a difference .
1642195848816.png
one is full domestic water pressure, hot water tank heating 50-60 lbs
and the other is usually 12-20 lbs tops heating
 

TheGreatSeagull

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Get one of these

Screw it onto the water heater drain valve and open the drain valve.

Read the pressure. It should be 80 psi or less.

Next step:

Leave gauge in place.

Run enough hot water to make the water heaters burner fire up. Roughly 10-15 gallons would be good.

Make sure no water is being used, no drips.

Watch the gauge as the water heater heats. It should NOT start rising in pressure.

If it does, that’s thermal expansion and it must be controlled. The most popular way is installing a properly sized thermal expansion tank and it charged to the correct air pressure.

It sounds like you’re experiencing thermal expansion to me......
So the pressure gauge is only reading at 30 psi.
 

hukre

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If you have a pressure regulator in the line to the house you need an expansion tank.
 
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