Which booster pump?

Discussion in 'Irrigation' started by jcom, May 9, 2007.

  1. jcom

    jcom LawnSite Senior Member
    Posts: 791

    We have a project with only 40 psi static psi. 3/4" supply pipe, 3/4" meter. Would like to install three rotor zones and two spray zones but will need to boost the psi.

    Any recommendations on which booster pump for this application?

    Thanks,

    John
     
  2. Dirty Water

    Dirty Water LawnSite Fanatic
    Posts: 6,794

    I don't think you need a booster pump.
     
  3. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 48,027

    What backflow will be used? Careful design could let you function with that 40 psi.
     
  4. jcom

    jcom LawnSite Senior Member
    Posts: 791

    We are using Febco 765 1" backflow. Hunter PGV 1" valves. 1" poly pipe throughout. Hunter PGP rotors, RBird 1804 sprays.

    I have not worked with this low of psi before. My understanding was that rotors will not work on psi less than 40. I figured with the psi loss at the meter, backflow, valves, pipe, and heads, that the rotors would not work with the approx. 33 psi I would have left. Regardless of design. I want to zone for 8-9 gpm.

    Thanks for all the help. I have been given the ok to add a pump to the cost. But if I don't need it, I won't use it and save the owner the cash.

    John
     
  5. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 48,027

    There is a basic problem that's common to all booster pump setups on small water supplies - the booster can out-pump the supply. I've seen this on pumps as small as 1/2 horsepower, when a faucet gets opened when the sprinklers are running. The faucet sucks air. You've created negative pressure in the house plumbing. If you install a whole-house booster system, that same negative pressure can exist in the supply line, which might be able to draw in contaminants. There are documented cases of this phenomenon.

    Hunter PGPs can work with 25 psi. You might be tweaking the radius adjustment screw, if the distribution doesn't look good. Don't count on a lot of distance.

    A better way to maintain pressure on a job like yours, is to employ antisiphon valves. You avoid the PVB pressure loss, and that 4-5 psi can come in handy.
     

  6. Oh my god, somebody actually advocating the use of a.s.v.'s.
     
  7. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 48,027

    Hey, if you need to preserve the pressure, it's an easy call. Not so easy to hide, if you need almost ten of them. Any backflow that works on gravity is okay in my book.
     
  8. jcom

    jcom LawnSite Senior Member
    Posts: 791

    Thanks, WB.

    I will give the ASV's a try and see what happens.

    Thanks for the info. Would you think I could get 25-28 ft. out of the PGP's with a #5 (2gpm) nozzle?

    John
     
  9. No complaints by me....just funny to see somebody else who would normally use an pvb and in line valves advocate a.s.v.'s. I thought the a.s.v.'s were just a CA thing.
     
  10. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 48,027

    It might be accurate to say a PGP may never spray, in feet of radius, the same number as there is psi at the head. So if you can run at 30+ psi, a 25 feet radius should be there. You might want to check the pressure loss numbers on the AS valves you can get. The lowest losses might still be with the Irritrol 2713 (2-3 psi at your flows)

    As an aside, I was always aware of some economies inherent in the AS valves, and now that the price of copper and brass has gone nuts, there will be a definite savings available with the AS valves. I often see small installs that could actually run from a faucet's water supply, and AS valves will be a way to lop a hundred bucks from the price, with nobody suffering for it.
     

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