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Discussion Starter #1
Hello,

I have a Reliance 501 47 gallon electric water heater. The T&P valve leaks when the top element cycles on. I have replaced the T&P valve, installed new thermoststs (upper and lower). I have turned down the water pressure to about 60psi. The (new) T&P valve leaks. The only way to get the T&P valve to stop leaking is to turn both thermostats to just above lukewarm. Thoughts? Very confusing!

Thanks,
 

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GC/Master Plumber/Mech
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While it's crazy even new parts right out of the box can be bad.

Replace the tpv with another new one..maybe a different brand.
 

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Discussion Starter #3
While it's crazy even new parts right out of the box can be bad.

Replace the tpv with another new one..maybe a different brand.

Will do. Dumb question..... Is there a short and long version of the T&P valve? The reason I ask is could the tip of the T&P valve be too close of touching the top element causing it to open?

Thanks.
 

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GC/Master Plumber/Mech
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I don't think so

Did you compare the lengths of the one you replaced with the new one?
 

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Discussion Starter #5
Yes and bought the same. Did not know if previous homeowner had previously replaced it or not.

Forgot to mention....I think the problem started when water company required the installation of a double check valve at the meter. Could I have an expansion problem?? Have not checked the pressure as the water heater does a complete cycle.

Is an expansion tank necessary if there is a checkvalve installed in the system?
 

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Plumbing Contractor
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They do make long and short shank T&P valves. Most water heaters require the short shank, but not all.

The fact that the t&p started leaking after the installation of a check valve indicates that there is an expansion issue. An expansion tank is necessary on a closed system which is what you now have. Previously, the water had a place to expand to...namely back out into the city main. Now that the system is closed due to the check valve, the water has no place for expansion. Install an expansion tank and I'm pretty confident your problem will be solved.
 
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