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Thread: Pressure tank question

  1. #1
    DIY Junior Member jackr's Avatar
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    Default Pressure tank question

    I have a Flotec tank on a deep well pump water system and the pump is cycling too quickly. It only takes 1-2 seconds to go from the preset 30 to 50 psi. I replaced the pressure gauge checked out the switch - all OK. When testing the pressure on the tank - should'nt the pressure be 28-30 when the gauge reads 30psi? Mine reads 23-24. Is this the cycling problem?
    This tank has been in service since '99. When its up to 50psi I dont get any drop in pressure 'till I turn on a faucet. If I have to add air - how should i do it, with no pressure in the tank or at the 30lb cut off. This setup was working well before. Is it possible for the tank to just loose pressure over time?

    Thanks
    Jack

  2. #2
    In the Trades Bob NH's Avatar
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    When the tank is empty of water the air pressure should be 2 psi less than the start pressure of the switch.

    It is very likely that your tank has failed; either the bladder, or the tank has a hole rusted through it. Nevertheless, here is a way to test it.

    First check the pressure gauge and tire gauge you are going to use by measuring the air pressure with the tire gauge and looking at the water gauge. THEY SHOULD BE THE SAME.

    If the gauges are not the same, here is a way to put proper air in the tank. After the pump runs and shuts off, shut the pump power off and SLOWLY release water from the tank until the pressure switch clicks to start the pump. Then measure the air pressure with the tire gauge.

    Now open the water drain and add air to the tank until the pressure is 2 psi less, as measured by the same tire pressure gauge, than you measured in the previous step.

    Shut off the compressor (or however you added air to the tank) and wait 30 minutes. Measure the air pressure again and if it has lost a lot of pressure then the tank or bladder has failed.

    You should get a decent pumping time after you recharge the tank. If the pumping time is shorter after a week or so then you have a failed tank.

  3. #3
    Moderator valveman's Avatar
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    It sounds like your bladder in the tank is bad. With the pump turned off and a faucet open until the tank is empty and the gauge reads 0, leave the faucet open and check the air in the tank with a tire gauge. There should be no water coming out of the air valve when you mash down on the valve core, and the tank should feel light and should sound hollow when you slap it.

  4. #4
    That's all folks! Gary Slusser's Avatar
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    IMO you should drain the water out of the tank. And if your tank doesn't have a drain you should add one.

    If you do the pressure check/adjustment without draining the tank, you will not get the right volume of air in the tank; pressure will read right, volume will be less than needed, the air cools and the pressure drops decreasing the air volume/pressure.

    I.E. a two story house with the tank in a basement and a faucet open on the 1st floor can cause the pressure to be off 4-6 lbs (.433 psi per foot of elevation).

    Setting the pressure at 2 psi less than cut-in... If you use an air compressor to add air, the compressor will heat and expand the air volume and when you turn on the pump it will fill the tank with colder water and that will cool the air dropping the volume/pressure some more. So I say 1-2 psi below the cut-in switch setting with no water in the tank and to be sure, then drain the tank and check the pressure after the air has been cooled.

    Tank manufacturers say that the primary cause of tank failure is incorrect air volume/pressure. It should be checked and adjusted annually. Low air volume/pressure causes short cycling of the pump and that increases pump starts and that increases the electric bill and kills pump motors.
    Gary Slusser Retired (= out of business)
    Click Here to learn how to correctly size or program a water softener.
    CAUTION, as of Nov 12 2013 all YouTube videos showing how to rebuild a Clack valve have an error in them that can cause damage.

  5. #5
    DIY Junior Member jackr's Avatar
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    Default Thanks for the replys ....

    There was no water coming from the valve stem when I checked the pressure. When I turned off the pump and drained the water out there was 0 pressure in the tank according to the dial gauge & the tire gauge. Is that right??? If I catch the pressure a on the dial at 30 should I then add air to the tank up to 28?

  6. #6
    That's all folks! Gary Slusser's Avatar
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    See my reply above your last post.
    Gary Slusser Retired (= out of business)
    Click Here to learn how to correctly size or program a water softener.
    CAUTION, as of Nov 12 2013 all YouTube videos showing how to rebuild a Clack valve have an error in them that can cause damage.

  7. #7
    Moderator valveman's Avatar
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    Your tire gauge should read 28, at the same time your dial gauge reads 0.

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