Design Problems

Discussion in 'Irrigation / Sprinkler Forum' started by ivseenbetter, Mar 27, 2007.

  1. ivseenbetter

    ivseenbetter New Member

    Mar 27, 2007
    I have been trying to figure out what to do in order to design my home sprinkler system. Basically, I am stuck on figuring out GPM. I did the bucket test coming from the spicket on the side of the house and the best I came up with is 5.5 GPM with 70 PSI. But when I called the water company to come out and test my flow because I thought that was way too low they told me that I have a flow of 25 GPM up to the meter after they tested it themselves. If I was to tap the waterline right after the meter for my irrigation system, would I basically be getting 25 GPM or does the meter slow down my flow to 5.5 GPM somehow?

    Any info is helpful. Thanks.

  2. jimbo

    jimbo Plumber

    Aug 31, 2004
    San Diego, CA
    Testing at the hose bibb..likely fed on a 1/2" line a long way from the meter, gave you the expected results. By the way, 70 PSI was the static pressure, but I suspect the dynamic pressure was substantially lower. This would NOT be a good place to tap off for the sprinkler.

    If you tap near the meter, and ran 1 1/4" pipe from there to the manifold, you could get your 25 GPM with very little pressure loss and an acceptible water velocity of around 5 FPS.

    By the way, at any supply store or even the depots, you can by a testing manifold rig which measures GPM and dynamic PSI. This could give you definitive results before you finalize your design.
    Last edited: Mar 28, 2007
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  4. ivseenbetter

    ivseenbetter New Member

    Mar 27, 2007
    Thanks Jimbo. I appreciate the info. I thought it was crazy to believe that I was really only getting 5.5 when the water company is telling me 25. I will probably do my plan based off of 20 GPM. That way I have a little bit of buffer built into it.
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