Replacing tank on vfd

Discussion in 'Pumps and Tanks Well Forum & Blog' started by greenmonster304, Mar 2, 2012.

  1. greenmonster304

    greenmonster304 New Member

    Joined:
    Apr 16, 2011
    Location:
    Hampton Bays, NY
    The tank for my vfd started to leak so I want to replace it but I am not sure what pressure to charge the new tank to. I wasnt sure if the vfd tanks get charged differently. Thanks in advance for your help.
     
  2. valveman

    valveman Moderator Staff Member

    Joined:
    Mar 15, 2006
    Occupation:
    Pump Controls Technician
    Location:
    Lubbock, Texas
    The tank precharge is usually about 30% less than the running pressure.
     
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  4. JPat

    JPat New Member

    Joined:
    Mar 5, 2012
    Location:
    Johnsburg, Il
    Hmmm. Every VFD we have installed, the manufacturer recommends 70% air pressure to running pressure...Doing the math for you; if your running pressure is 60psi the pre-charge in the tank should be 42psi.
     
  5. valveman

    valveman Moderator Staff Member

    Joined:
    Mar 15, 2006
    Occupation:
    Pump Controls Technician
    Location:
    Lubbock, Texas
    Hi JPat. Doing the math I think 70% of, or 30% less than 60 is still the same 42 PSI. The real question is why did the tank go bad?
     
  6. JPat

    JPat New Member

    Joined:
    Mar 5, 2012
    Location:
    Johnsburg, Il
    Meh, tanks go bad all the time. The rubber that most companies are using is recycled... "Do it yourself" tanks have a high failure rate as well. 5yr warranty on all tanks!!!
     
  7. valveman

    valveman Moderator Staff Member

    Joined:
    Mar 15, 2006
    Occupation:
    Pump Controls Technician
    Location:
    Lubbock, Texas
    Bladder or diaphragm type tanks only go bad for two reasons. Either they rust through, or the bladder breaks. Most of the busted bladders I see on tanks with a VFD, are from the pump not shutting off when it should, causing the pressure to spike and bust the bladder.

    One of the big box stores has a 32 gallon tank with a lifetime warranty. I guess it doesn’t have recycled rubber.
     
  8. Texas Wellman

    Texas Wellman In the Trades

    Joined:
    Feb 9, 2010
    Occupation:
    Owner of a Water Well and Pump Repair Business
    Location:
    SE Texas-Coastal
    "Lifetime warranty"...when it breaks, the life is over!!
     
  9. greenmonster304

    greenmonster304 New Member

    Joined:
    Apr 16, 2011
    Location:
    Hampton Bays, NY
    The tank rusted out because it was in a pit that was always damp.
     
  10. valveman

    valveman Moderator Staff Member

    Joined:
    Mar 15, 2006
    Occupation:
    Pump Controls Technician
    Location:
    Lubbock, Texas
    Good to know. These are the kind of installations that can benefit from a fiberglass tank.

    Yeah "lifetime warranty". Can you believe that? I think the company might just change names every few years to get out of warranties. :)
     
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