Which heads for river source?

Discussion in 'Irrigation' started by jcom, Jul 5, 2006.

  1. jcom

    jcom LawnSite Senior Member
    Posts: 791

    Our customer has a 3 hp pump rated at 76 gpm at 30 psi and 92 gpm at 40 psi. We need to lift 5 feet and push to the highest point about 35 ft. Two inch discharge and suction. We are thinking our 255 sx will not pull 2" line so will have to rent a bigger machine. Ideas?

    Longest zone is approx 400 feet away. Close zones about 40 feet away. Each area to be watered is approx. 130 x 150 ft. Four areas relatively the same size. We want to use some big heads that will throw a long ways. What are the best choices? We use Hunter and Rainbird heads for our residential installs but want the best head for the job. Customer doesn't care if we have precise coverage just that is mostly getting water. A dry spot here and there would not be a problem per his statements.

    Any help would be appreciated.

    John:waving:
     
  2. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 48,027

    Care to look at those pump numbers again? Big heads need big pressure. A single stage centrifugal won't give you that. Can you loop a mainline? You can pull 2 inch poly with the right blade on a 255sx.

    Starting from scratch, you'd use a different pump. A multistage jet pump would be able to supply 20 gpm at 70 psi (Goulds HSJ20) - that's enough flow to cover a couple of acres, and the flow is compatible with pipe you can pull.

    If you had to go big, you would need to get more pressure, and would be adding a second pump in series with the first. Not economically feasible for two acres of lawn.

    I'd guess Rainbird heads as being most crud-tolerant, on account of their seals. The R-50 is about the one head that could actually function on low single-stage-centrifugal pressures, not that you'd be thrilled at the distance they throw at 25 psi or less. But they would pop up and rotate reliably.
     
  3. Worked on a 9 zone system a few weeks ago that was on a well. I changed a 205 valve that would not close because of fine sediment in the valve. The system originally had R-50's and PGP's had replaced some of the R-50's. I ended up replacing 3 R-50's that had quit rotating but still had a strong stream. I ended up cleaning 3 PGP filters because of weak streams but still rotating. This system had about 40+ rotor heads and most are now PGP's.
     
  4. PurpHaze

    PurpHaze LawnSite Fanatic
    Posts: 5,496

    Sounds like some type of filter for the supply water is in order.
     
  5. The well runs the house water also . I suggested a filter to the homeowner and he said it had one, so I left it at that.
     
  6. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 48,027

    River water would be organic crud, instead of sand. More annoying than destructive. R-50's could blow it through without worries. Most rotors could. Used to be that pumped surface water meant impact heads only.
     
  7. jcom

    jcom LawnSite Senior Member
    Posts: 791

    Yep, WB, my numbers are transposed. Damn, you don't miss a thing. :)

    I have only glimpsed the pump as it was in a storage shed under a bunch of junk. The owner gave me the specs from the pump after he had it dug out and out in the open. I am relatively new to pumps supplying the water for irrigation although I have some service customers that have them.

    I know that it is a centrifugal pump. I will have to go and have a look. Is it most likely a single stage or is that the only kind of centrifugal pump? He wants to use that pump and I am trying to figure out how to do just that.
    I believe I could loop a mainline around the property although he mentioned he would like the valves close to his house so that may not be an option. Wouldn't we still have a pressure issue with a looped mainline?

    It would seem that it is a high volume/low pressure pump if I understand at least a little. Where would the application be for something like this?


    Your patience is commendable!:waving:


    John

    We use a lot of PGPs but always with 50-70psi.
     
  8. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 48,027

    The idea of a looped mainline is to basically cut the mainline pressure loss in half. If you do want to utilize the full capacity of that old pump, you'd need to use more material than a different pump might cost. That pump might be more compatible with four-inch aluminum irrigation pipe, like you see used above ground on farms.

    Almost no one ever really utilizes the flow capacity of a straight centrifugal pump on an irrigation system, since the performance curve shows the best flows at 30 psi or less, and you need many more heads to cover an area at lower pressures. I remember seeing a jury-rig of two 3/4 HP centrifugals in series outperform a neighbor's 3 HP centrifugal. When the two 3/4 HP pumps died, a single 1 1/2 jet pump was used. to replace them, and worked even better.

    My two pump recommendations would be a Goulds JS15 (1 1/2 HP jet pump) that can give 20 gpm at 50 psi, and the HSJ20 mentioned earlier. (2 HP three-stage jet) - those pumps are mostly for 20 to 25 gpm, based mostly on the case dimensions (1 1/4 suction and 1 inch discharge)

    Another poster mentioned a Sta-rite (Berkeley) 2 HP multistage, and it shows higher capacities, and has larger suction and discharge openings.
    http://www.starite.com/specs/berk_b2094bk.pdf

    These are not cheap pumps, but the extra pressure should justify the purchase price. Mind you, I would love for the homeowner to pony up a few thousand extra, just to make a system fit that straight centrifugal pump.
     

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