Pumping from catchment

Discussion in 'Irrigation' started by lowvolumejeff, Jul 11, 2008.

  1. lowvolumejeff

    lowvolumejeff LawnSite Member
    Posts: 72

    Homeowner has groundwater spring(s) piped to an underground 750 gallon cistern. He wants to use it to irrigate his lawn and shrub beds. The cistern is a length of concrete conduit and is placed horizontally. It is 18 " to the top of the water in the cistern, and about 4 feet to the bottom. The empty cistern recharges in about 3 hours. The suction head is 5 feet. The maximum discharge head is 20 feet. The water recharging is remarkably clear, however there is a fine silt buildup at the bottom of the cistern.

    questions:

    1) what type and HP pump would you recommend?

    2) What type of filtration?

    3) What type of spray heads should I use?

    Thanks in advance. Jeff
     
  2. Mike Leary

    Mike Leary LawnSite Fanatic
    Posts: 21,606

    Find out what the recharge is before you get carried away, 750 is not much storage.
    You'll need a clock that has multiple programs/delay between zones or ISC.
    It's tricky, but it can be done.
     
  3. lowvolumejeff

    lowvolumejeff LawnSite Member
    Posts: 72

    Thanks mike. The recharge rate is 3 hours. Jeff
     
  4. Mike Leary

    Mike Leary LawnSite Fanatic
    Posts: 21,606

    Missed the point..got to figure the re-charge vs. the demand. Roughly, I have one with
    a 6gpm charge...got some big demand turf zones....for every 20 min of run, rest 1 hour.
    Get my drift?
     
  5. lowvolumejeff

    lowvolumejeff LawnSite Member
    Posts: 72

    Mike: Not sure I understand. I may be approaching this incorrectly. Here is an attempt to explain my thinking (a dangerous undertaking - at best). If I design the system based on , say 6 GPM, with recharge, that would let me run it approximately 75 minutes (350 gallons in catchment plus recharge of almost 100 gallons). For practical (and fudge factor insurance) I would probably only run it for 60 minutes. Boots recommended Maxipaws in another thread with silty water supply, so if I wanted to, I could run 4 with a 07 LA @ 25 PSI for an hour, let the cachment recharge, and run another zone in 3 hours. I plan to sell him on a WM SL1600 with all the whistles and bells.

    I am hoping for other options as to which spray heads to use. Think what i could do with MP's and proper filtration. Also, I am aware that increasing the PSI, throws my plan off as at 35 PSI the same head increases output by 0.4 GPM. Of course this allows me to use 3 heads per zone = more zones, and I can sell him more modules,etc..

    Thanks for your help, it is appreciated. Jeff
     
  6. Dirty Water

    Dirty Water LawnSite Fanatic
    Posts: 6,799

    Your recharge rate is roughly 4 GPM (750 gallons / 180 minutes).

    If you shoot for a reasonable 10 GPM, You'll get an easy 75 minutes of watering with the water currently in the tank, During that time, the recharge will bring in an additional 570 gallons, so you have a 240 gallon buffer.

    This leaves you with a 2 hour recharge time to bring the tank back full.

    I'd set it up to water on odd/even days and have a one hour delay between rotor zones. On sprayheads pushing 10 GPM you probably don't need to much of a refill delay, maybe 15 minutes.

    I'd run Rainbird 1800's, avoid VAN nozzles as they clog easily. I'd also add a rusco spindown silt screen on the pump output.
     
  7. Mike Leary

    Mike Leary LawnSite Fanatic
    Posts: 21,606

    Something you can't avoid with cistern systems is daytime runs, I try to run drip &
    shade spray zones then.
     
  8. lowvolumejeff

    lowvolumejeff LawnSite Member
    Posts: 72

    Well, DUH. Should have known recharge rate expressed as GPM would clearify things. As you can see, I don't do wells. Interested in learning more however.

    Has anyone a suggestion for pump size and type? Jeff
     
  9. Dirty Water

    Dirty Water LawnSite Fanatic
    Posts: 6,799

    A small one :)

    I'm not a pump expert, perhaps Wet Boots can weigh in, otherwise I usually trust the local pump guy to pick the appropriate pump when I can give him the lift, desired GPM and pressure.

    Some how this thread has ended up being entirely pacific northwest people. Odd.
     
  10. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 46,459

    I think you wind up using some midget jet pump, and a lot of zones. One basic question, is the 4 gpm enough to water the areas desired. (If it's more than an acre, forget the whole thing)
     

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