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Thread: Cistern addition questions

  1. #1

    Default Cistern addition questions

    Currently I have a well that produces 2.5 gal/min only 70 ft. deep. I also have a cistern located on the property 1000 gallon concrete. It is not currently in use. we did however just clean and inspect it and it is in good shape. I would like to use it to increase the storage for irrigation of 80x80 ft. lawn. My thoughts were to run a new water line from the well to the cistern and install a float switch to control water level in the cistern. Then install a pump in the cellar where the pressure tanks are to maintain the pressure of the house. I have read that it is good to put a submersible pump in the cistern instead of pulling water. The cistern is above the pressure tanks by 8 ft. So I was thinking of using a jet pump. The water line to the cistern is in place already. I would then disconnect the old water line at well which is about 200 feet away and 30 feet higher in elevation than the pressure tanks.

    The well pump has I believe a pumptec control that protects against dry running and pauses the startup for whatever minutes you choose. Is it possible to install a pressure switch at the well itself and a float valve instead of a float switch? If so,I would not need to run electrical to the cistern from the well.

    Thanks in advance,
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  2. #2
    DIY Hillbilly Southern Man's Avatar
    Join Date
    Jun 2008
    North Carolina


    It looks like you are creating a cross connection from the cistern strage to the well. I don't think that you want to do that.

    Is the cistern outside? If so, why not fill it from your roof leaders and have a separate plumbing system just for irrigation?

  3. #3
    In the Trades Bob NH's Avatar
    Join Date
    Oct 2005
    New Hampshire


    Since you want to use the well for both irrigation and household, you will want to keep the well pump the same. I would design a system as follows:

    1. Install a check valve in the existing line just after the tee to the branch that goes to the cistern. The check valve will prevent water from flowing back to the cistern.

    2. Run a new line from the pump to the cistern as you have shown. That line can come off anywhere between the pump and the check valve.

    3. Put a solenoid valve and a check valve in the line from pump to cistern, and put a float switch in the cistern.

    4.Connect the float switch and the pressure switch in the following logic, using relays:
    a. If pressure switch closed OR float switch low THEN Pump on.
    b. If pressure switch closed THEN solenoid valve closed; ELSE solenoid valve open.

    The effect of the contol logic in (4.) above is that the pump will supply the pressure tank if the switch is calling for pressure and will fill the cistern when there is no demand from the pressure tank.

    Now you can put an irrigation pump on the cistern. It will cost less than a submersible pump. The cistern is isolated from the household system. The well pump will supply water at a higher rate, with saving in power, than it supplies to the pressure tank. The well pump is protected by the Pumptec.

    If you have a second source of water for the cistern then you can use it without contaminating the household water.

    Post again or send me a PM if you decide to go this way and need help with the relay logic.

  4. #4


    Thanks Bob,
    I understand the logic behind the relays. I could actually put the check valve and the solenoid valve in the cellar before the line goes out to the cistern. There is an existing float valve in the cistern already. If I understand correctly then could I use a pressure switch (instead of a float switch) that is set to open the solenoid valve ( and fill the cistern) only when the pressure tanks are fully pressurized. If the pressure drops in the tanks (I have 2 ) then the solenoid valve closes. I am trying not to have to run electrical from the cellar under the asphalt that goes all the way around the house to the cistern. I can get power for an irrigation pump to the cistern but connecting into the cellar is a bit of work.

    Southern man,
    I would disconnect the line so as not to connect back to the pump. We only get an inch of rain/ month during july-sept.


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