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High Pressure System 2000 Storage Tank

Phonso Member Posts: 2
I noticed high pressure 160 in some cases higher on the inlet of the DHW storage tank from the plate. And a dripping relief valve which is rated at 150 psi. Sometimes HW faucets release high pressure and sometimes drip. I first noticed high pressure of a 100psi on the cold domestic water feed back through the gages at the water filtration system. I have since installed a back flow check at the water make up to the storage tank and now the feed is a constant 60psi with no issues.

The water storage tank line from the DHW Out plate still has a periodic high pressure. I thought about installing a DHW expansion tank, but 160 psi is still a problem as 150psi should be the max.

Could the storage tank be overheating while system is in a zone heating mode? I opened the 150 psi relief valve to see how much water would flush out and noticed little water coming out but has a stead drip when closed. Any thoughts? I think is a brain challenger.


  • Robert O'Brien
    Robert O'Brien Member Posts: 3,541
    If you installed a backflow preventer or check valve, you created a closed system. Needs a domestic expansion tank
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  • Jamie Hall
    Jamie Hall Member Posts: 23,321
    If you install a domestic water expansion tank, set for the normal domestic water pressure (you mention 60 psi) the high pressure on the hot water side will go away.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • szwedj
    szwedj Member Posts: 66
    edited April 2
    Comments from @Robert O'Brien and @Jamie Hall are spot-on about installing a domestic expansion tank, and it should be located on the cold feed to the tank, after your flow check and before the tank. As far as domestic water temperature, the domestic out of the plate during a domestics hot water call should be between 130F-140F. There is either and external spring check above the domestic circulator or and internal flow check in the domestic circulator which should prevent the tank from over heating during heat calls. If the domestic out is getting hot during heat call, there is a good chance that this flow check will need to be replaced. And if your tanks relief valve is still dipping when the pressure is below 150# you should replace it.
    Joe Szwed
    Energy Kinetics
  • Phonso
    Phonso Member Posts: 2
    Thank you all for your input. I installed the domestic expansion tank. System pressure bang on 60psi.  I will replace the relief valve since it's old and has a slight drip with normal pressure and temperature.  Water filtration is perfect.  And I added a leak detection system with an App.  I appreciate this group.  Thank you.