Below Ground Irrigation Tank Pump Recommendations?

Discussion in 'Irrigation / Sprinkler Forum' started by ACEBOHRMAN, Dec 29, 2007.

  1. ACEBOHRMAN

    ACEBOHRMAN New Member

    Messages:
    3
    Location:
    Central Coast, CA
    I recently installed a 2500 Gallon below ground water tank to catch rain water from the gutter drains on that side of the house to feed 6 zone irrigation system described below.
    I will tie into my irrigation system with 1" PVC.
    I have 20amps / 115AC available near the tank.
    Irrigation system is comprised of 6 zones averaging (3) 5gpm sprinkler heads.
    I believe 30 PSI will be sufficient pressure to run 2-3 zones at a time.
    The bottom of the water tank is 9'-10' below highest sprinkler head.
    The system is currently fed from city meter water through an
    above ground anti-siphon valve.

    Using this info. can someone recommend a pump type and model to adequately power this system?
    How about an inline filter to prevent clogging of the sprinklers and some drip lines although the water should be fairly clean since it goes through a catch basin with 1/8" screen before entering the tank?
    Great Forum! Thanks in advance for any recommendations.
  2. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    http://www.waynepumps.com/manuals/WLS_Series.pdf

    Your request to run 3 zones at a time adds up to 2400 gallons per hour. With the 9' head, you would be right on the edge with the 1 hp pump, which will run on a 115v @20 amp circuit. You would be better served with the 1½ hp, but that would require a 25 or 30 amp circuit at 115. A better idea is to either arrange to have 240 for the motor, or rethink your zoning. With the array of timers available, there is really only a need to run one zone at a time. You can easily cover any size of property using timers and appropriate zoning.
  3. Bob NH

    Bob NH In the Trades

    Messages:
    3,317
    Location:
    New Hampshire
    You need to look at your requirements to see what you need.

    Your water supply is limited to a 2500 gallon cistern.

    How often does it rain to collect 2500 gallons of water? How many gallons per week can you rely on getting? Are you going to fill the cistern with city water when it doesn't rain?

    You want to run 2 or 3 zones at a time with an average of 3 sprinkler heads at 5 GPM each. Let's consider 2 zones at 15 GPM per zone. That would require a 30 GPM pump, which will empty the tank in 83 minutes.

    A more reasonable pump would do one zone at a time so it must supply the largest zone with 30 psi.

    A 1/2 HP Goulds 13GS05 submersible pump will deliver 16 GPM with a little margin for 30 psi, and it can be throttled to 4 GPM without distress where it will provide about 65 psi.

    A 3/4 HP Goulds 18GS07 submersible pump will deliver 25 GPM with the same margin and can be throttled to 6 GPM where it will provide 75 to 80 psi.

    Shallow well jet pumps would give you 16 GPM for a 3/4 HP Goulds J7S and and 21 GPM for a 1 HP Goulds J10S. The could operate as low as 3 GPM without a problem and probably lower.

    A 1 HP Goulds G10 Irrigator pump would give you 30 GPM at 30 psi with a little margin. It is described as a "self priming centrifugal" but such pumps can be a problem to prime.

    With any of the above you can operate them without a pressure tank if you use your valve control system to operate the pump. You must have a relief valve on the submersible pump, piped back to the tank or installed in the line where it comes out of the pump. You should have a relief valve on the other pumps if you operate without a pressure tank and switch; piped to return to the cistern.

    The cistern should settle out any sand large enough to plug the sprinkler heads and the screen on the pump inlet should catch anything like leaves or plastic that might get into it. I would not add a filter.
  4. ACEBOHRMAN

    ACEBOHRMAN New Member

    Messages:
    3
    Location:
    Central Coast, CA
  5. Wet_Boots

    Wet_Boots Sprinkler Guy

    Messages:
    798
    Location:
    Metro NYC
    If you really want to employ a cistern for lawn watering, consider severing the city-water connection. Interconnecting city water and ground water, if indeed you can even do it in California, can only be effectively done by way of an RPZ backflow preventer ($$$) which may subtract enough water pressure to ruin performance. Figure on using that year-round stream, if you can get away with it. If you have the acreage, all the pumps and strainers and backflow preventer money will be worth it. For smaller lawns, cistern watering is probably going to cost more than city water.
  6. ACEBOHRMAN

    ACEBOHRMAN New Member

    Messages:
    3
    Location:
    Central Coast, CA
    I am already using a Wilkins 720a Pressure Vaccuum Breaker to prevent backflow. Meter water runs around $80/ month additional during the dry months (June-Oct) to water the 1/4 acre garden, no lawn, mostly drought tolerant shrubs, and a few plants that need a fair amount of water, ie. roses, ferns, begonias, fushias. Water shortages are a problem here and I expect the cost to keep going up, hence the cistern. Thank you Wet Boots. I be able to wean off of the meter completely.
  7. Wet_Boots

    Wet_Boots Sprinkler Guy

    Messages:
    798
    Location:
    Metro NYC
    PVB = no good for your cistern project. RPZ only need apply (same toxic-backflow protection, plus the backpressure protection the PVB does not possess) ~ Another factor in the use of a cistern is making sure mosquitos can't breed in the water (West Nile Virus concerns)
  8. Gary Swart

    Gary Swart In the Trades

    Messages:
    7,396
    Location:
    Yakima WA
    You'd better make sure you can draw water from that stream legally. That sort of thing is very tightly regulated at least where I'm located.
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