Pressure Tank Pressure

Discussion in 'Pumps and Tanks Well Forum & Blog. Water is life.' started by Honestfletch, Jan 2, 2005.

  1. Honestfletch

    Honestfletch New Member

    Jan 2, 2005
    I Have read several posts (threads) re: Pressure tanks and I just want to make sure I have my facts straight

    1 - My Water Pressure is very Low
    2 - My Cut in pressure for my pump is set at 20 psi
    3 - When the pump is off (at full pressure) the PSI Reading on the pressure tank is at 45 psi
    4 - If I were to set the pressure tank to the correct settings, I would turn off the Pump, drain the pressure tank - put in 18 psi of air - turn the pump on with the water shut off to the house (Allowing the pressure tank to fill and build pressure).
    5 - My only concern is that logically, as the tank gets full of water, the pressure will go well beyond my tire guage's scale. I do not want to blow anything up! :cool:

    Is it safe to assume that If I follow the above steps, that my pressure tank won't blow up?

    Thanks in advance for any advise
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Sep 2, 2004
    Retired Systems engineer for defense industry.
    New England
    The pump pushes water into the tank compressing the air bladder until it reaches the upper pressure setting on the control. This also has the advantage of storing some volume of water in the house so that the pump doesn't have to turn on to provide pressure. Assuming that the pump control is working (it turns off at the proper time), you won't blow anything up! I'm not sure how a pressure tank is specified - there is probably some way to calculate good turnon/turnoff set points and size of a tank to provide a reasonable volume to minimize short-cycling the pump.

    Having no air in the tank causes many problems as can having the wrong pressure in the tank.
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  4. Deb

    Deb Plumber

    Sep 5, 2004

    You are doing okay until we get to #5 (which is not logical ;-).
    The function of the pressure switch is to turn the pump on and off at the pressures set on the switch--in your case, apparently 20-45, a 20# differential is recommended. And all pressure tanks should have a pressure relief valve in case of a malfunction where the pump does not shut off.
    You cited low water pressure at the beginning of your post....the only thing that will help is a higher on/off pressure (with corresponding change in the tank air pressure). Unless there was a reason not to (like a very deep well with a marginal pump or critical water levels in the aquifer), I would recommend that you consider a 30-50 or a 40-60 pressure switch. Make sure that your pump is capable of the increased work load before you make this change, however.
    The Pipewench
  5. Gary Slusser

    Gary Slusser That's all folks!

    Aug 31, 2004
    Wherever I park the motorhome.
    The air pressure in the tank when the pump shuts off equals your cut-out pressure switch setting. IOWs you're checking water pressure only. That's why when checking the air pressure you do so wit hno water in the tank; so you get the proper volume of air in the tank which then provides the pressure to move water out of the tank when the pump is off. It's the power stored in the compressed air in the 'pressure' tank that moves the water then.

    Quality Water Associates
    Last edited: Jan 8, 2005
  6. dwpecksr

    dwpecksr New Member

    Sep 27, 2004
    owner Dale's Plumbing Service inc
    pump pressure

    You say you have little pressure? If you install a 40/60 pressure switch shut down the well (electric) and get the pressure down to zero. Install a new pressure guage to make sure you have correct readings. put 38lbs of air in the tank. If you have any filters, you may want to change them at this time. check all the areators on your faucets for calcium build up. you didn't say if you had low pressure throughout the house or just on certain faucets. :)
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