Improving pressure for sprinkles...

Discussion in 'Irrigation / Sprinkler Forum' started by Crest, Jan 23, 2008.

  1. Crest

    Crest New Member

    Messages:
    3
    Location:
    Cairo, Egypt
    Dear all,
    I'm using a 1HP Lowara pump with a ball,lifting water from 7m deep well, for my irrigation network...
    it's divided to 2 separate lines with valves, each line has 16 "Rain Bird 15van" sprinkle...
    puting into concideration that I operate one valve each time, the pressure isn't enough to raise the sprinkles to operate properly!!!
    someone told me to add another ball... will that increase pressure effectively??? another one told me to replace it with 1.5HP or even 2HP pump...
    plz. advice the cheapest way...

    Thanks...
  2. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    Your 15VAN nozzles will put out about 3.5 gpm each if set to full circle, and even assuming the average set at 1/2 circle, that is 1.5+ gpm EACH, or about 24 GPM total. Is your pump rated at 24GPM ( ~1500 gallon per hour) at 25 PSI?
  3. Bob NH

    Bob NH In the Trades

    Messages:
    3,317
    Location:
    New Hampshire
    It isn't clear what a "1HP Lowara pump with a ball" is and I have no idea what the pressure/flow characteristic is. Can you test the flow and pressure capacity of the pump by measuring the flow when the pressure is about 25 psi? I don't know what metric scale you use, but that is about 18 meters water column.
  4. masterpumpman

    masterpumpman New Member

    Messages:
    729
    Location:
    Virginia Beach, VA
    To much lift!

    Without knowing the specific mode of your 1HP Lowara pump I suspect it is a lawn sprinkler pump pumping from 7 meters (23 ft). This pump is not capable of building enough pressure for your sprinkle heads at that depth. More HP won't help. You may need a multi stage pump or Jet Pump to get the pressure you need.
  5. Crest

    Crest New Member

    Messages:
    3
    Location:
    Cairo, Egypt
    Recommendations help...

    many ppl told me that 1.5 HP of the same pump will be ok, u can check it in this site: http://www.lowara.com/lowdata/doc/EN/bg-ed-en.pdf , puting into concideration that my existing pump is PGM 7 , and the recommended pump from others is PGM 11, would u think it will be ok or what...
  6. Bob NH

    Bob NH In the Trades

    Messages:
    3,317
    Location:
    New Hampshire
    Based on the curves at the link you gave us, both of the pumps you mention are limited to about 32 liters per minute (about 7 US gallons per minute) at 7 meters lift. Those little tails on the chart labeled 8m, 7m, 6m, et cetera represent the limiting lift values corresponding to the flows, beyond which there is not enough Net Positive Suction Head (NPSH) to prevent cavitation in the pump. In other words, the pump can never pump more flow than the chart values for those values of lift.

    You must limit the number of sprinkler heads so that they don't exceed the rated flow rate of the pump at the pressure for which the heads will operate.

    The BG7 pump will deliver about 40 psi at that flow and the BG11 pump will deliver about 50 psi. That is enough pressure to operate most sprinkler heads.

    But if the total demand of all of the sprinkler heads exceeds about 32 liters per minute, then none of them will work properly.

    Because of the FLOW RATE LIMITATION OF THE PUMP, neither of the pumps will work for the number of heads that you have. More horsepower will not solve the problem for that model of pump.

    When selecting a pump it is important to get one with a SUBSTANTIAL MARGIN OF SAFETY for the NPSH requirement, because any little problem can cause it to fail. For example, warmer water will decrease the suction lift capability of the pump.
  7. Crest

    Crest New Member

    Messages:
    3
    Location:
    Cairo, Egypt
    Thanks for help...but still confused...

    :rolleyes:thanks Bob NH....

    but i've been thinking of another solution, maybe work or not...
    puting into consideration that i use the same pumb for home use...
    can i get another pumb let's say 1HP without pressure tank, to work as a pooster to the main pumb ?? and to operate as pass by the main pumb, wich i only operates both with sprinklers and i operate the main one only with home use ?? what do u think ????:confused:
  8. Bob NH

    Bob NH In the Trades

    Messages:
    3,317
    Location:
    New Hampshire
    The "Main pump", the one that you described in the beginning, can't lift more water from the well at the flow capacity beyond 32 liters per minute. Putting another pump after it is not likely to help that.

    How much pressure will the existing pump deliver if the sprinklers are not turned on? Are you pumping to a pressure tank, or just into a pipe system?

    The link you gave us it to a page that describes a BG Series pump, which is described as a centrifugal pump. It shows a BGM7 and BGM11 pump where they differ only in that the BG7 pump uses a three-phase motor and the BGM7 pump uses a single-phase motor.

    Your description says you have a PGM7 pump. Note the difference; PGM7 or BGM7. Is it just a typo or should I be looking for a different kind of pump? I have found another link that suggests it is a Jet pump; because the description says it has a built-in ejector. http://www.lowara.com/products/product.php/2665?dt=bg#dxf

    Instruction Manual: http://www.lowara.com/lowdata/doc/ml/surface-im-xx.pdf
    Last edited: Feb 10, 2008
  9. michel1

    michel1 New Member

    Messages:
    5
    As far as I am concerned water pressure for your sprinkler is low just because of elevation difference. So you just need to adjust the place of sprinkler.
  10. Daltex

    Daltex New Member

    Messages:
    15
    Location:
    Texas
    Crest,

    You must chose between the right pump or the correct flow rate of the sprinkler heads. If the pump is used for your house then getting a mega pump might be to much for the house but adequite for the sprinklers.

    Just add more zoning or better yet use lower flow rate nozzles on your sprinkler head. You can get the same throw distance with less volume to equal what others said is the maximum. You will just need to water longer to make up the the decreased flow rate.
  11. shag_fu

    shag_fu New Member

    Messages:
    31
    Location:
    Illinois
    Another option is to cut your zone size down. That many heads is kind of at the limit for normal flow. Since you have subnormal flow either changing heads or increasing the number of zones might be cheaper than buying a new pump. That also depends on how many zones you currently have and what your controller can handle. This is why pressure should be checked and verified before laying out your zones.
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