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PSI for irrigation system

Discussion in 'Irrigation' started by Ray Kane, Dec 30, 2006.

  1. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 47,673

    No one is lifting water thirty feet, in any practical application of a standard centrifugal pump. Even twenty-five is a stretch. In order to evaluate both pump and well, you must remove any restrictions from the outlet of the pump, and install a nipple and a tee, with a pressure gauge, and a gate valve, and an elbow and some more pipe for a horizontal discharge. You also can use a vacuum gauge to view conditions on the suction side of the pump. Operating the pump with the discharge partially closed will give you varying outlet pressures, and you can measure the flow, usually by the bucket method. (I might use a 30 gallon trashcan on a pump this size)

    You should always pump the well for at least an hour, with an eye on the gauges, to see how the water table is holding up.
  2. drmiller100

    drmiller100 LawnSite Senior Member
    Posts: 562

    i've done sprinklers before where the "lawn" had 75 feet of vertical change. It was on a "hill."

    I will totally agree that you can't suck more then 20 feet or so, but you CAN push it quite a bit, and it does subtract from either volume or pressure available to the sprinkler head.
  3. Ray Kane

    Ray Kane LawnSite Member
    Posts: 16

    Long post but please take it all in

    Spoke with neighbor - he took a lead weight and string, lowered it down his pipe and heard a splash at 12 feet. Our houses are 300 feet from each other and at the same elevation. He then attached a 2" PVC 90* for a 10' horizontal run to the pump suction side.

    On the output side a 1.5" run 14' long goes to a hydrotek 4-zone index with 1 inch outputs.

    Now for the interesting part. A lizard met its demise in the hydrotek. We did an R&R on the hydrotek and left the index stuff out by mistake. When we turned on the pump it ran all four zones with no problem.

    Both of our homes have approx 5000 sq ft of area to be watered.

    Currently I have a similar setup except for the output side. I have a 1.5 inch "T" with a 3/4" hose bib on top and a 1.5" ball valve on the side.

    Any suggestions before I continue?
  4. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 47,673

    The curve that was posted shows an operating range as high as 60 gpm, so powering four zones with a lift of less than 15 feet is not unreasonable.
  5. Ray Kane

    Ray Kane LawnSite Member
    Posts: 16

    Is it possible to run it as one zone? The front and back yards are the only areas which need coverage. Both side yards have pavers and gravel. The pump is located in the direct center of the side yard so all I would have to do is "T" off the 1.5" output to the front and back.
  6. katienpdx

    katienpdx LawnSite Member
    Posts: 5


    As with any field working with pumps requires an understanding of the terminology common to their applications.

    Pump performance is measured in volume as gallons per minute (GPM) and in pressure as head. In general a trade off occurs between head and flow with an increase in head causing a decrease in flow and vice versa.

    Head refers to gains or losses in pressure caused by gravity and friction as water moves through the system (see figure below). It can be measured in lbs/in2 (PSI) but is most commonly listed in feet of water.

    Static Suction Lift - The vertical distance from the water line to the centerline of the impeller.

    Static Discharge Head - The vertical distance fromthe discharge outlet to the point of discharge or liquid level when discharging into the bottom of a water tank.

    Dynamic Suction Head - The Static Suction Lift plus the friction in the suction line. Also referred to as a Total Suction Head.

    Dynamic Discharge Head - The Static Discharge Head plus the friction in the discharge line. Also referred to as Total Discharge Head.

    Total Dynamic Head - The Dynamic Suction Head plus the Dynamic Discharge Head, also referred to as Total Head.

  7. bicmudpuppy

    bicmudpuppy LawnSite Silver Member
    Posts: 2,781

    How many heads are you planning? what nozzles? in other words, how many GPM? This pump has a listed max operating pressure of 40psi. even with minimum restrictions for backflow, lateral piping and zone valves if needed, your going to be down to 30psi at your heads. And, if your lifting aprox 15', your max discharge with a 40psi at the discharge point (before pressure losses in the plumbing) is 20gpm. The chart posted is from the pumps specs. right before that chart is the chart with the pumps discharge specs with relation to lift and desired pressure. With less than 5' of lift, yes this pump would push 60 plus gpm, but your only going to get 10 psi. The pump spec page is here

  8. Ray Kane

    Ray Kane LawnSite Member
    Posts: 16

    Are the specs the same for my pump {DS2HF-192PL} and the PD series pump?

    Front yard will be 6 full spray heads, 10 1/2 spray heads and 4 1/4 spray heads.

    Back yard will be 6-8 rotors

    How much do I lose due to the 2" check valve?

    Anyone have advice regarding zone indexing and pump timer controls?
  9. speedbump

    speedbump LawnSite Member
    Posts: 117

    The guys are right about 25 feet being the maximum lift that pump can do. Your 1.5hp pump is way oversized for a 1" zone. You might want to run several at the same time depending on the ability of your well to produce water. If it were mine, I would be using a smaller pump. Why waste all that amperage when you can only use a maximum of 25 gpm without the friction loss going totally off the chart. At 35 psi with a 12 foot lift, that pump wants to be putting out 40 gpm. At 25 gpm the friction loss is already around 15 lbs. through a hundred feet of 1" pipe. The H in the model number means High Head, so this pump can make more pressure than a Medium Head pump. But it still can't overcome the friction loss.

    Don't worry about losses through a check valve, you can't use all the water this pump is able to produce anyway. And I doubt your well can produce that much water anyway. You should cut the pipe leaving the pump and do the bucket test to see what the well is capable of, then go from there.

    The only thing I can see beneficial about the garden hose is for priming the pump initially. Other than that, it's kind of useless for any sort of testing.

  10. Ray Kane

    Ray Kane LawnSite Member
    Posts: 16


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