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Thread: bladder tank -whats up?

  1. #1

    Default bladder tank -whats up?

    I have put a new bladder tank in my sons house and it does not seem to be filling with water. I took it off line and looked in the inlet for a plug or something that might be blocking it but all I see is what appears to be the bladder which I would guess to be normal.I put it back online and the tank stays empty -feels like no water at in it.Of course the pump cycles on and off like crazy . Do tanks come bad from the factory sometimes or am I missing something? thanks

  2. #2
    Retired Defense Industry Engineer jadnashua's Avatar
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    You need to precharge the tank with the appropriate amount of air. This should be ~2 pounds LESS than the turn-on pressure of the pump control. SO if it is set to 30/50, it would be set to 28#. tO do this, you need to shut off the pump, open a valve and let the water run until it stops leave it open until you finish, then pump up the tank (or bleed off some air). SHut the valve and and turn on the pump and see what happens.
    Jim DeBruycker
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    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    Our bladder tanks come from the north east part of the country. I assume the elevation up there is much higher than here in Florida. The tanks that say they have a precharge of 38 psi. Sometimes have a precharge of around 50. If that's the case with your tank and your switch is set at 50 or below, your tank will not take in a drop of water.


    bob...

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    In the Trades Bob NH's Avatar
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    "Our bladder tanks come from the north east part of the country. I assume the elevation up there is much higher than here in Florida. The tanks that say they have a precharge of 38 psi. Sometimes have a precharge of around 50."

    If you charge the tank to a specified gauge pressure at high altitude, the gauge pressure when measured at lower altitude will be LESS than the original setting.

    EXAMPLE:
    At high altitude (atmospheric pressure of 12 psia), charge to 38 psig; the absolute pressure will be 50 psia.

    Measure the gauge pressure at sea level (14.7 psia); the gauge pressure will be 50 psia - 14.7 psia = 35.3 psig.

    There isn't any manufacturing place in the northeast that is higher than about 1000 ft. That will make a difference of less than 1 psi if you measure the pressure in Florida.

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    Alright; so explain the higher than labeled pressure.

    bob...

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    In the Trades Bob NH's Avatar
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    "Alright; so explain the higher than labeled pressure."

    The factory quality control process is not perfect. They probably set the regulator wrong or some guy who couldn't read the instructions grabbed the wrong pressure labels.

    Maybe someone incorrectly converted kPa to psi.

    Whatever it was, it was not caused by any variations in atmospheric pressure.

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    I guess you have to give it to them for being consistant!

    bob...

  8. #8

    Default thanks for replies but...

    I have done that-set the air pressure to around 2 below the cut in -but the tank does not seem to accept any water. The tank is still very light and system pressure is around 50 psi so I think the tank is not accepting water but could be wrong.I will try again your advice to make sure it is correct.Also my pressure switch only has a high cut off -low cut off is built in according to that.Is that normal or should I invest in a better switch which has both. thanks again to all who reply.

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    Retired Defense Industry Engineer jadnashua's Avatar
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    Maybe it would be good to tell how you set and adjusted the pressure. You must do it with the pump off and a valve open. Double-check the piping, sometimes the galvanized stuff can get messed up with rust. Same is true for the input to the pressure switch - it must be clean or it will have trouble sensing the water pressure properly.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    Once the pump shuts off, how much water comes from the tank before the pump turns back on again?

    bob...

  11. #11

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    In re-reading the first post, boboiatl says he looked in the inlet and saw what he assumed to be the bladder. I don't think I've ever seen the bladder looking at the inlet elbow. Any thoughts?
    Ron

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    Maybe he stuck his finger in the elbow. I guess you could feel the bladder.


    bob...

  13. #13
    Moderator & Master Plumber hj's Avatar
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    Default bladder

    The inlet should not have an elbow. When removed from the system any bladder tank with more than zero pressure will expand to fill the tank. It deforms/compresses as pressure pushes against it.

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    We are referring to the elbow on the bottom of practically all bladder tanks.

    bob...

  15. #15

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    Thanks Speed.... I was pretty sure bladder tanks had an elbow on the bottom....
    If the bladder was distended bad enough to be seen from the elbow, I'm sure the tank needs to be replaced.
    Ron

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