Expansion tank on water heater

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Old 02-07-19, 02:46 PM
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Expansion tank on water heater

My water heater is brand new. I just replaced it after my old water heater of only two years leaked everywhere due to pressure issues. I installed a PRV on the new one and my pressure is now 60 PSI. Had an expansion tank installed after that because my T&P valve kept going off, spewing hot water. My expansion tank product #PFXT5 has a pre-charge pressure of 40 psi. My T&p valve STILL continues to sporadically spew hot water out of the outside drain!!!! Annnnd my T&p is hot to the touch! My plumber said the expansion tank is fine. However, I contacted another company for a second opinion and they stated that my pressure is 60 PSI so my expansion tank needs to be the same pressure (60psi) too. I called my plumber and he said no the expansion tank is fine because it has a pre-charge pressure of 40 psi that goes up to 150 or whatever. What should I do? What are your recommendations? What is your expertise? The new company is recommending me to change my expansion tank to match my pressure of the home (60psi) and have a new T&p valve placed.
 

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Old 02-07-19, 04:07 PM
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Are you sure that the expansion tank is preset to 40-60 PSI and does not have water inside it when the system is depressurized (turn off main water and open a cold faucet upstairs and now measuring 40 PSI in the tank)? Although presetting to approximately the static water pressure (no one using water; 60 PSI in this example) is best, it should not be going overpressure if the preset was 2/3 of that.

Using a bike pump (or more rapidly using a small air compressor) you can raise the PSI of the existing expansion tank without dismounting it.

While modifying the expansion tank preset pressure also have the main water turned off and a cold faucet open upstairs.
 

Last edited by AllanJ; 02-07-19 at 04:24 PM.
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Old 02-07-19, 04:13 PM
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Welcome to the forums.

The pressure tank needs to be charged to the same pressure as the cold water house pressure is. The tank maximum is 150psi. Once that is done..... your T&P valve should be fine. The link below is the installation manual for that tank. It also mentions keeping the water temperature under 150.

Proflo Thermal Expansion Tank (pdf)
 
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Old 02-09-19, 10:53 AM
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My plumber said the expansion tank is fine. However, I contacted another company for a second opinion and they stated that my pressure is 60 PSI so my expansion tank needs to be the same pressure (60psi) too. I called my plumber and he said no the expansion tank is fine because it has a pre-charge pressure of 40 psi that goes up to 150 or whatever.

You need a new plumber. I am no plumber and I still know PJ is giving you the straight scoop. The tank needs to be set to the same pressure as the incoming water pressure.
 
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