Cistern pump control switch

Discussion in 'Pumps and Tanks Well Forum & Blog' started by NealinNevada, May 7, 2007.

  1. NealinNevada

    NealinNevada New Member

    Messages:
    7
    hi to everyone :) ! I need to control my well pump to fill my cistern (2500 gal plastic tank on a 30' tower). Currently I have a timer do it, but I need to automate the filling of the cistern by the amount of water in the cistern. Needless to say, I have no desire to go up on the tower any more than I have to. I was wondering if someone could recommend a really good float switch to turn the pump on/off that will last for years. I am assuming that the use of a float switch is appropriate, but if there is a better solution, I am all ears..."tanks" :D in advance folks!
  2. speedbump

    speedbump Previous member

    Messages:
    4,540
    Location:
    Riverview, Fl.
    I like to use 24 volts to do this. A piggy back float switch, a transformer than plugs into the wall, a few male/female electrical plugs and some wire. The piggyback floats come with 10 or 20 foot cords.

    bob...

    Attached Files:

    Last edited: May 7, 2007
  3. NealinNevada

    NealinNevada New Member

    Messages:
    7
    Bob...Thanks for the sketch...I can see the safety side of your drawing and that was the approach I was thinking of. My major problems are these:

    1) I want to put in a system that will withstand years of being in the cistern (I'll pay more for better quality without blinking). I have done some reading and I guess I need a pump up switch (is that correct?? normally closed unless the switch is tilted upward), and

    2) I have no way of knowing who makes a really high quality one, and

    3) Do you know anyone who sells them?

    Much appreciated Bob!:D

    ON EDIT: Does anyone make a pressure switch that I could install in my pump house (directly below the cistern) where it could read the pressure of the water in the 1-1/2" outlet pipe of the cistern. So maybe it comes on when it sees 5 psi and turns off when it sees 10 psi? This would avoid having to put a controller switch in the cistern (which I dread climbing up to do).
    Last edited: May 7, 2007
  4. Rancher

    Rancher Guest

  5. Bob NH

    Bob NH In the Trades

    Messages:
    3,317
    Location:
    New Hampshire
    USA Bluebook has a large selection of switches.

    I would use a mercury switch such as the
    https://usabluebook-onramp.com/cgi-bin/onramp.exe?custnum=&password2=&pgm=unixgrep.bbx&itemdesc=48428&image.x=25&image.y=8

    https://usabluebook-onramp.com/cgi-bin/onramp.exe?pgm=itemdet.bbx&id=48428&custnum=RETAIL++++&password=&sesid=0507195400

    Get one with a long enough cord so you don't have to splice and put a relay at the bottom where you can change it if necessary. The mercury switch is very reliable and is not a hazard when it is in a sealed unit.

    They have others if you want to search.

    USA Bluebook accepts credit card orders and ships UPS same day if you order by 5 PM Central Time.

    If you are using a pump to pump OUT of that tank, you may want to put in a pump-down switch connected to protect the pump if you run out of water.

    The switch at the link is a SPDT model that can work in either pump-up or pump-down mode.
  6. speedbump

    speedbump Previous member

    Messages:
    4,540
    Location:
    Riverview, Fl.
    My sketch shows a solonoid valve not a relay. If you want the pump to turn on and off by pressure, you need a pressure switch and a tank. Then the solonoid valve will open and close depending on the water level in the cistern. There are more than one way to do this job, it's up to you which one you prefer.

    I don't know what horsepower or voltage your pump is, but I would be leary of turning on/off a pump with the float only. You should have a definate purpost contactor along with the float if this is what you intend to do.

    I sell the float switches and they are as good as any of the ones advertised above, just less expensive.

    bob...
  7. Bob NH

    Bob NH In the Trades

    Messages:
    3,317
    Location:
    New Hampshire
    If you use a definite purpose contactor (which is a big relay) then the pump will operate with less pressure and you will get more gallons per kWhr.

    For a 7 ft diameter tank you will have about 150 gallons per pump cycle for 6 inches of level difference in the tank.

    Compare the complexity and cost:

    Level switch required for both systems. Get one with a cable long enough that you don't need to splice it anywhere in the run from the float switch to the relay. I usually put the cord through a 3/8" hole in the flat part adjacent to the manhole in the tank.

    Case A: Add a definite purpose contactor which costs about $25 for a 30 amp model.

    Case B: Add a tank ($200), pressure switch ($15), and solenoid valve ($25 to $100 depending on size and type).

    I always go with the relay/contactor.

    You can probably mount the contactor in an electrical box if it is protected. If the motor is small you can get an enclosed relay that will handle up to 1 HP at 240 Volts.

    If you use 24 Volt control (nice if you are uncomfortable with 120 Volts in the tank) you will need a 24 Volt transformer for either system (About $15). The transformer can mount on or in the box with the relay/contactor.
  8. valveman

    valveman Moderator Staff Member

    Messages:
    4,549
    Location:
    Lubbock, Texas
    When using a solenoid valve to fill a storage tank, the pressure can be just as low, and the pump just as efficient as when using the pump start relay. You just need to use a large enough solenoid valve (1"), with no other restrictions, and the line will be wide open to the storage tank. You are already lifting water 30' so, this will make the pressure just as low, and the pump will use no more electricity than with a relay. You may even need to hold back a little pressure while filling the tank, to keep the well from pumping dry to quickly. Less gallons per Kwh would probably only mean a buck or two extra per month.

    However, either method will work fine.
  9. speedbump

    speedbump Previous member

    Messages:
    4,540
    Location:
    Riverview, Fl.
    Definate purpose contactor $19.85, Tank $143.12 (42 gallon), Pressure switch $12.96, 1" Solonoid valve $18.33.

    bob...
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