My pump is pulling water from an underground holding tank to service my house. There was an air leak in the line so the pump was pulling air along with the water, but I believe I have found and fixed the leak. However, my pump cycle time has shortened considerably and there is an associated apparent loss of water volume (two flushes and the pump cycles, when the tank should have a 20-25 gallon water capacity in a 40 gallon pressure tank). Is it possible that the air has partially filled my bladder, and if so, how to purge the air?

Thanks for any help or suggestions-- MZ

2 Answers 2

  1. Turn the pump off at the breaker
  2. Close the valve from the tank to the house, if you have one.
  3. Drain from the valve that is normally on the tank tee for the purpose, or the lowest point in the piping connected to the pressure tank with a drain. Any air trapped on the wrong side of the bladder will come out.
  4. Check the air pressure in the tank with the water pressure at zero. Adjust to 2-3 PSI below your pressure switch cut-in. If it's very low or zero, you have a bladder failure (or an old-fangled non-bladder tank, where you would want air to be sucked in, so, probably not applicable.)
  5. Close the drain, turn the pump back on. Wait for it to shut off.
  6. Drain into a bucket, recording the volume. Stop draining when the pump turns back on.
  7. Compare the volume drained to your tank's chart for the cut-in-and cut-out pressures you have set.
  8. Open the valve to the house.
  • You can do just 1,2,3 & 8, but might as well do 4,5,6,7 while you're there.
    – Ecnerwal
    May 9, 2023 at 15:36
  • Thanks for the info, I will give 1,2,3, and 8 a try and see what happens. That is the procedure I thought would work but wanted to throw the question out there to get another opinion. The tank is only a year old so I don't think there is a bladder failure yet. The tank's location is below grade level which makes it difficult to drain, so the less times I drain it and haul buckets of water out of the crawl space the better! The "help" line in my Pentair paperwork is useless, all I get is a recorded "this number has been disconnected" message, and their website is no help either.
    – user166677
    May 11, 2023 at 12:52
  • 4 does not require any hauling of water. And will reveal the actual state of the bladder rather than making assumptions.
    – Ecnerwal
    May 11, 2023 at 12:59

Short cycle time is due to TOO LITTLE air in the system. The tank needs to be mostly air when "empty" so that the air can compress and maintain a reasonable amount of pressure as water is pumped into the tank.

The bladder is there to prevent the air from being absorbed into the water and getting lost. Helpful is a special air valve that sucks in a little air every time the pump runs. (I can't remember the name of this valve -- it's been about 40 years.)

  • A snifter valve is used only on non-bladder tanks, if you are sufficiently old-fashioned and into self-made misery to have a non-bladder tank.
    – Ecnerwal
    May 9, 2023 at 22:49

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