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Water hammer question

Discussion in 'Irrigation' started by AI Inc, May 18, 2008.

  1. AI Inc

    AI Inc LawnSite Fanatic
    Messages: 26,616

    How come when a customer has had a system working fine for yr. If the pressure tank on the houses boiler is replaced it always seems to create water hammer when the system starts.
    I had 1 call like this last week and another for this tuesday .

    Last 1 I changed the wires so drip would come on first instead of last reducing water demand and speed.
    Next weeks dosnt have any drip and I may need to nozzle down the #1 zone.
  2. DanaMac

    DanaMac LawnSite Fanatic
    Messages: 13,185

    Could it have caused an air pocket or something?
  3. AI Inc

    AI Inc LawnSite Fanatic
    Messages: 26,616

    Not realy sure but I have seen this about 25 times in the last 10 yrs.

    Messages: 18,668

    They sell hammer arrestors at HD. Never had to use one but have recommended to people to try out.
  5. Valveman

    Valveman LawnSite Member
    Messages: 53

    The new pressure tank probably has too much air charge.
  6. AI Inc

    AI Inc LawnSite Fanatic
    Messages: 26,616

    Ive tried these in the past with no success.
  7. Waterit

    Waterit LawnSite Silver Member
    Messages: 2,930

    Find the preload pressure of tank, then drain and check to make sure it's 2PSI
    under cut-in.
  8. WalkGood

    WalkGood LawnSite Bronze Member
    Messages: 1,910

    I'm doubting that, if it is a hot water heating system. They operate on a closed system with reduced pressure via a PRV typically set to 12 psi (sometimes slightly higher if it is a 2 or 3 story residence).

    Now if it is on a hot water HEATER (domestic hot water) then the pressure tank will be a higher psi and usually matches your house water pressure. However the domestic water shouldn't be higher than 80 psi. Any more and things like toilet fill valves can blow out.
  9. AI Inc

    AI Inc LawnSite Fanatic
    Messages: 26,616

    Second call was the same. Guy replaced the pressure tank on the domestic over the winter.I turned down the ball valve on the backflow and set a delay between zones. See if that does it.
  10. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Messages: 50,259

    Is there any check valve downstream of the POC? I could see a benefit to having one.

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