Well pump sizing?

Discussion in 'Irrigation' started by jason1313, Jul 7, 2006.

  1. jason1313

    jason1313 LawnSite Member
    Posts: 2

    In building a new house, we told the builder we wanted to up-size the pump in order to install sprinklers after we moved in. Turns out they forgot to consult with the well driller. The pump that is installed is a Gould's 3/4 horse. the well cap says 300' casing 60' the line supplying the house is only 1" sch 120. After talking with the builder they say we should get about 12 GPM (did not know pressure other than 40/60 switch installed) with this pump. and to upgrade the pump would be about $1400 extra. They would foot the labor because of their mistake. Is it worth 1400? that sounds way high to upgrade a pump! (I do not no what upgrade defines yet either) what size pump do you guys recommend for new construction? 2 acres only watering front half though (1 acre)
     
  2. speedbump

    speedbump LawnSite Member
    Posts: 117

    You can run a sprinkler system on 12 gpm. You simply design the sprinkler system to it.

    $1400 sounds a bit steep but maybe not in your particular area.

    There is also the thought that maybe your well won't support a bigger producing pump. Check with the driller.

    bob...
     
  3. Ask the well driller what the recharge rate of the well is and work from that.
     
  4. lawnmaniac883

    lawnmaniac883 LawnSite Silver Member
    Posts: 2,613


    Better yet ask him what the drawdown on the well is.
     
  5. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 48,027

    In general you don't get your money back on a pump upgrade. You're usually going to have the same heads in the same locations, so the system you'll install won't be much cheaper. But it won't have to run as long, and that might have value.
     
  6. jason1313

    jason1313 LawnSite Member
    Posts: 2

    thanks for all your responses, looking at the paperwork from the driller, It reads; the well was pumped for 30 minutes at 20+ gpm, a 12 gpm pump was installed. So now i need to do a bucket test and check what pressure and gpm to design my system to correct?
     
  7. WetWell

    WetWell LawnSite Member
    Posts: 59

    If you know the pump model and the depth of the well you can determine the flow at the maufacturers website. I wouldn't go by what the driller says as I have had a couple that were wrong on the wells they did.

    Then you can compare what the manufacturer says the what you actually get at the site to see if it is operating properly.
     
  8. speedbump

    speedbump LawnSite Member
    Posts: 117

    You need to know the depth to water, the depth of the well is totally unimportant for a pump test. Just unhook the pipe at the well, install a valve and a gauge, fire up the pump, valve the output to 40 psi. and check the gallons per minute. Do this after letting it run for 10 minutes wide open.

    bob...
     
  9. WetWell

    WetWell LawnSite Member
    Posts: 59

    Yes it is depth of water that matters, I assumed he would know that [the charts ask for that]. He might as well let that pump run for five hours and see if it is OK as he has a huge area to water, one acre will need a pool of water.
     
  10. speedbump

    speedbump LawnSite Member
    Posts: 117

    That might be true in his area. Here if it runs steady for 10 minutes, it's good for the duration. But we have rock wells made in pourous limerock so the amount of water you can get is endless. Screened wells and some of the other types may give different amounts after pumping for a long time.

    bob...
     

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