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Volume but no pressure

Discussion in 'Irrigation' started by ATV, Jul 16, 2011.

  1. ATV

    ATV LawnSite Member
    Messages: 44

    Hi Guys,

    I installed four 36" sand-points and plumbed them all together, equidistant from each other and the pump. Then from the well, I ran 2" irrigation pipe 400 feet to a manifold where I'm attaching garden hoses to run garden sprinklers.

    I had to locate the well so far away because that's where the water is.

    Currently I have a 1HP sprinkler pump that is rated for upwards of 33 GPM. No tank.

    I have a lot of water volume at the manifold but there is not enough pressure to run even one sprinkler. My goal was to be able to run 4 sprinklers at once.

    What do you guys suggest in order to improve the pressure? Should I be looking at a shallow well pump with a pressure tank instead of an irrigation pump or perhaps a larger pump?

  2. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Messages: 50,517

    How do you know the "sprinkler pump" is any good? What testing (flow and pressure) did you perform near the pump discharge?
  3. ATV

    ATV LawnSite Member
    Messages: 44

    Its brand new.
  4. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Messages: 50,517

    Skruw brand new. It could be perfect, and your assembly technique might be the issue. How do you know that you have no suction leaks?

    And one more time. What flow and pressure testing did you do right at the pump itself?
  5. ATV

    ATV LawnSite Member
    Messages: 44

    I haven't tested it but its got to be putting out at least 15 GPM.
  6. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Messages: 50,517

    You should simplify your life and install a shutoff valve upstream of the 400-foot main. and run some tests at the pump. You could even use a vacuum gauge to observe operating conditions on the suction side.
  7. regularguy

    regularguy LawnSite Member
    Messages: 152

    You have left out a lot of details that would be very helpful.

    400 feet is a long distance for a 1 horse pump, I pump water from 3 sandpoints slightly longer than 400 feet and use a 1 1/2 horse pump and a 2 horse pump, the smaller pump discharges into the larger pump to increase the pressure. I also have 30 feet of rise in the distance so that needs to be factored as well, I don't believe that you mentioned rise only distance.

    As others have said I would ensure that the pump out put is acceptable at the source and then increase the pump size to provide the pressure that you desire, but I'm pretty confident that it will be more than a 1 horse pump, also how deep are the sandpoints? That also has a huge impact on the pump performance.
  8. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Messages: 50,517

    another possible factor is a craptastic home cheapo pump with a service factor of 1.0 on the motor
  9. ATV

    ATV LawnSite Member
    Messages: 44

    Thanks. That's most helpful.

    Good news. It turns out that pipe dope from installing the system had made its way to the sprinkler heads and clogged them. I cleaned out the heads and now have 4 sprinklers running at one time. As I turned on each new sprinkler it didn't seem to affect the water pressure on the others (not that I could tell anyway) so it appears I have decent pressure.

    My points are 11 feet deep plus 3 feet of point. I'm right on top of the clay so can't go any deeper. Clay is 33 feet thick. However, the water table is 18 inches. Its right next to a swamp. We'll have to see. No guarantee it won't dry up on me but short of going down 70 feet or better it was the only option I had.

    I may consider going to a larger pump. I'll know better after I run this one longer.
  10. WalkGood

    WalkGood LawnSite Bronze Member
    Messages: 1,910

    If you go larger you could suck more water than can be replenished in that shallow source. Esp in dry season.

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