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Need Help. Rainwater Harvest to Irrigation?

Discussion in 'Irrigation' started by FNCPonds, Mar 7, 2009.

  1. FNCPonds

    FNCPonds LawnSite Member
    Messages: 46


    I am installing a 5000 gallon rain water harvest system in the ground hooked up to a pondless waterfall. There will be a 1/2 HP pump hooked up to the main hose from the waterfall as well as a shut off valve to the waterfall pump.

    So I guess what I need to know, how can we run a system that when water in the pit is to low the sprinklers will turn on from the main line instead of the water fall reservoir.

    Thanks for any and all
  2. mitchgo

    mitchgo LawnSite Silver Member
    Messages: 2,922

    First depending on your regulations you have to have a RP installed ( reduced pressure backflow assembly) on your POC for your irrigation to prevent cross contamination to the potable water.

    There is several ways to do it. The proper way is pretty expensive regarding installing sensors in the tank. installing relays. master valve for the city water ect.

    If it was my house I would go the cheap way and just install a simple isolation valve between the city water and pump tank water. a warning sensor in the take if it is low. Making sure I had a rp installed.

    Messages: 18,668

    I posted a thread on a system I inspected that had a similar situation. Since you are tying city water in with RW you will need an RPZ device (I think, but a high hazard bcflw device for sure) at the city hookup. Don't try and sneak this by the city. Check codes obviously. If you are pumping from the RW reservoir then the city water will need to be used to keep that at a constant level say the 1000 gallon level of the reservoir.
    Stolen from A-1 Maybe BIC or somebody will weigh in with some type of switching mechanism that when the reservoir drops below a certain level a master on the city water opens up. Seems to me though for the sake of simplicity having the irrigation always coming from the reservoir and the city water being used to keep water available in the reservoir would be the way to go. I've never done this just surmising. The other option is to use manual gate valves to determine where the water comes from.
    Last edited: Mar 8, 2009
  4. AI Inc

    AI Inc LawnSite Fanatic
    Messages: 26,616

    You can use a float vale , like the type used in a sump pump ( only backwards of course) to refill the cistern with city water when the level drops.
  5. BrandonV

    BrandonV LawnSite Platinum Member
    Messages: 4,583

    the easiest way is probably just have your city water fill the receiver. you can do this with a simple float valve, that way there won't be the need for the ho to go our and change valves and relays from the pond source to the city source. also no cross contamination.
  6. Sprinkus

    Sprinkus LawnSite Silver Member
    Messages: 2,297

    R.P. should be installed at the water meter to protect city water supply from contamination, along with an expansion tank in the house to prevent build up of excess pressure in the house lines. (Typically the excess pressure from thermal expansion caused by heating water will just travel back into the city main, an R.P. installed on the house line would prevent this from happening).

    What type of pump will be used to run the irrigation? A submersible pump or an above ground booster pump?

    A typical design that I would do would require three electric float switches and would use the tank as the source for all irrigation water:
    One will need to be set slightly above the pump intake, or foot valve, to shut off the pump in case the water in the tank gets too low. (This protects the pump from running dry).
    A second one will be needed to turn on the supply of potable water to supplement the tank when the tank gets low. (This one is set slightly above the one that protects the pump).
    A third one will be used to turn off the potable supply when the tanks fills to a predetermined level. (This one is set above the second one to allow enough water in to keep up with irrigation but still leave enough room for rainwater to be collected).
    Last edited: Mar 8, 2009
  7. Sprinkus

    Sprinkus LawnSite Silver Member
    Messages: 2,297

    Well, after thinking about this and remembering the last job I did I came up with this design that only needs two float switches:

    Attached Files:

  8. BrandonV

    BrandonV LawnSite Platinum Member
    Messages: 4,583

    Just realized how poorly I typed that. Please forgive me ML.
  9. Mike Leary

    Mike Leary LawnSite Fanatic
    Messages: 23,097


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