Expansion tank Pressure setting

Discussion in 'Pumps and Tanks Well Forum & Blog. Water is life.' started by Onokai, May 12, 2021.

  1. Onokai

    Onokai Member

    Joined:
    Apr 19, 2012
    Location:
    Arcata,Ca
    I'm adding a small 2 gallon expansion tank to my 80 gallon solar water heater which feeds my 40 gallon gas water heater, I.m putting it in the incoming cold water line from well with a 40-60 pressure switch.
    What air static pressure should the tank have in it charged before the install 38#s? of split the difference at 50#s?
    Thanks
    mark
     
  2. Reach4

    Reach4 Well-Known Member

    Joined:
    Sep 25, 2013
    Location:
    IL
    I was going to say 60, which would be the right answer if there was a check valve in the path.

    If there is no check valve, I could see 40 or 50, which might minimize reverse flow through your softener.

    I have no check valve and no expansion tank, so my 44 gallon pressure tank takes up the expansion. The main downside is that there is some phantom water use registered by the softener as a result.

    So optimum would be 60, but add a check valve between the softener and the WH. I am undecided what to choose if you have no check valve.
     
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  4. valveman

    valveman Cary Austin Staff Member

    Joined:
    Mar 15, 2006
    Occupation:
    Pump Controls Technician
    Location:
    Lubbock, Texas
    With no check valve between the WH and well pressure tank, you don't need an expansion tank.
     
  5. Onokai

    Onokai Member

    Joined:
    Apr 19, 2012
    Location:
    Arcata,Ca
    I put in a check valve as I have a spun calcite tank that gets the well water first and I want the back pressure off this tank so the one way valve is a few feet past this tank before expansion tank. The reason I'm adding this tank after 39 years is my solar water collectors on roof (for 39 years) can get pretty high presure when overheating before the older style drain down valve kicks in.The sytem is pretty complex as this solar roof collectors loop into the 80 gallon tank as well as i recently added my own solar electric ground array and use some extra power to also heat a 3500 watt element in same 80 gallon solar tank as the hot water collectors feed into. I also have past the water heater the newer grundfus smart hot water loop pump for insatnt hot water at all home taps.The solar loop pipe rattle a bit now and then so I thought the expansion tank will help this condition. The well is 140 feet away downhill.
    I'll set that presure at 60 psi-thanks for the replies
     
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