what size pressurized water tank?

Discussion in 'Pumps and Tanks Well Forum & Blog' started by Noahsoak, Aug 30, 2009.

  1. Noahsoak

    Noahsoak New Member

    Messages:
    7
    have an old galvanized water tank - small tank possibly only 32 gal. maybe 40 the flow test on the well when i bought house shows only 6gpm from well. what size pressure tank should I buy? am thinking of just leaving old tank in place and just tying in the new tank (suggestion from neighbor) then he said, i would have both tanks with water so the pump would have to come on less frequently - 1/2 hp pump

    the psi (?) is 40/60 - a well guy came out to install a new tank - but there was no room to get one in, the old tank is in a closet in a mud room - so he showed me how to open the tank to get air in (no shrader valve) - to cure the water log problem - he saved me alot of dough -

    my neighbor has offered to help me with it - but i am unsure of the size i should buy

    thanks for your input
  2. valveman

    valveman Moderator Staff Member

    Messages:
    4,588
    Location:
    Lubbock, Texas
    If you have smelly water you need to stay with the same size and kind of tank. If it is just a galv tank because it is an old system, you can switch to a bladder tank. Switching to a bladder tank means you have to do away with the air charge components.

    If you switch to a bladder tank, you can use a Cycle Stop Valve and then you only need a 4.4 gallon tank as in the one pictured above.
  3. Gary Slusser

    Gary Slusser That's all folks!

    He probably measured the 6 gpm through a 1/2" drain valve at the tank.

    If so, that is not an accurate way to determine the gpm. And that is what you use to size a 'bladder' type tank.

    Is your 1/2 hp pump a jet pump or submersible? Do you know anything about the well depth of pump depth? What diameter well? Static water level?
  4. nhmaster

    nhmaster Master Plumber

    Messages:
    3,189
    Location:
    S. Maine
    You should put the largest tank in that will either fit or that you can afford. Larger tanks = longer pump cycle times. Longer pump cycle times = less $ for electricity to operate and longer pump life. The only exception would be if the well could not produce enough water to fill the tank but that's pretty rare. One more thing. Drop the pressure switch to 30/50. 40/60 is pushing it for a shallow well pump.
  5. valveman

    valveman Moderator Staff Member

    Messages:
    4,588
    Location:
    Lubbock, Texas
    I use to be an advocate of larger tanks but, not anymore. You will actually get longer cycle times, which means longer pump life, when using a CSV and a small tank. The longer run times for small amounts of water might increase the electric bill a couple of bucks but, you can’t save enough to ever pay for the added expense of the larger tank.

    Manufacturing pumps and tanks uses a lot of energy, and making pumps last longer and reducing the tank size required will also save energy. This savings just shows up as a decrease in overall cost of materials, instead of actually on the electric meter.
  6. Noahsoak

    Noahsoak New Member

    Messages:
    7
    what size pressurized water tank

    when we bought this place this is what the flow test report said
    casing size 6 in. static level 14 ft.
    depth 200 foot (per seller) - pump depth 100 ft.
    pipe dia. @ well head 1 inch
    test times start 1 pm - stop 6 pm

    test comprised an unrestricted discharge and regulated discharge, both at well head

    unrestricted disc. indicated well is capable of supplying 8 to 10 GPM
    regulated disc. performed at 4 hour period at rate of 6 GPM

    system produced 6 GPM consistently over 4 hour test - pressure tank is a small 40 gallon tank without a bladder

    that's the skinny

    the well/pump guy that came out - suggested 32 gal. steel tank
  7. Noahsoak

    Noahsoak New Member

    Messages:
    7
    what size pressurized water tank

    forgot about the pump type - this is a 4" submersible pump - 1/2 hp
  8. valveman

    valveman Moderator Staff Member

    Messages:
    4,588
    Location:
    Lubbock, Texas
    Then I would suggest at least a 32 gallon tank. And since the well man suggested a steel tank, he probably knows there is something in the water that needs to be mixed with air to prevent smelly water. If that is the case, don't use a bladder tank.
  9. Gary Slusser

    Gary Slusser That's all folks!

    IMO the test is showing the well recovery rate.

    I've never seen an OK 1/2 hp submersible pump deliver only 10 gpm open discharge with a static water level of 14'. And then only 6 gpm "regulated discharge" unless he all but shut the 'regulating' valve off.

    I suggest a CSV instead of a much more expensive pressure tank that you don't have space for anyway.

    And if you have iron in the water, don't use a "Steel" air over water tank. Doing so will cause rusty water.
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