gpm test

Discussion in 'Irrigation' started by AVERDEROSA, May 14, 2005.


    AVERDEROSA LawnSite Member
    Posts: 17

    I do all kinds of landscaping been in the bussiness for 15 years. I im trying to install a small sprinkler system at my own house. I have done some research so i am not clue less. But I tried the bucket test and it takes 45 seconds for me to fill a 5 gallon bucket from my spicket. I have 65 psi at the spicket. I also did the same test at my nieghbors house with the same results. What is the problem?
  2. Dirty Water

    Dirty Water LawnSite Fanatic
    Posts: 6,799

    Pressure and volume are not the same.

    Design you system around 6 gpm and 65 psi.(Or use a pressure reducer) Look at your heads nozzle charts.

    AVERDEROSA LawnSite Member
    Posts: 17

    I was told by the sprinkler supply that at my gpm under 7 gpm I would only be able to run two sprinkler heads in a zone. They told me I need more like 13gpm. Also spoke to my local water company and they said I should be at like 15gpm. I dont understand why my gpm is so low.
  4. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 47,697

    Try connecting the pressure gauge to a different hose bibb than the one you fill the bucket from. Also, check to see if you have a pressure reducer in the house plumbing. If you are doing your own work at your own house, you have the luxury of doing the plumbing first, and doing a flow test from it. Even if you only have that 6 gpm, you can work with it. Likely, you will have more.
  5. justgeorge

    justgeorge LawnSite Senior Member
    Posts: 352

    Keep in mind that filling a bucket from an outdoor faucet is only coming from probably a 1/2" copper line. Assuming you're tapping into your main with at least a 3/4" line (then bumping up to 1" either before or after the backflow) and your GPM will be higher.

    Good luck!

  6. kerdog

    kerdog LawnSite Member
    Posts: 129

    Hey AVERDEROSA-----

    Another thing to consider. What is your supply line from the source? Copper, galvanize, pvc? How old, what size? You can pressurize any size line, quarter-inch or 2", or whatever size. But, that size line will help determine what gpm you can get. It could be, if galvanized, and old, that deposits have built up over time, and now that 'three-quarter' line, is only half-inch inside, or smaller. Hence, not enough flow, no matter the pressure. Galvanize is REAL bad about doing that.

    See ya---kerdog
  7. bicmudpuppy

    bicmudpuppy LawnSite Silver Member
    Posts: 2,781

    Ok, do you have more than one hose bib? Open them both and then time how long it takes to fill the bucket. I'm betting you will still fill the bucket in about 45 seconds. 1/2" service line running who knows how long from the main will only carry about 6 or 7 gpm at best. I usually figure 1/2" pipe at 5gpm max. and that includes swing pipe in a run of more than 2'. Yes, you can get 6+ gpm through swing for a full circle rotor, but not if you have a very long run of it.
    If you get 6gpm from one bib with both open, then you probably have the 13 that the water district is telling you is supposed to be there.

    Where are the TX lic. irrigators at for this thread? Doesn't anyone size pipe anymore? Yeah, I know I don't either. The cost of reducers and inventory keeps it from being cost effective. (do see lots of cheap !^%@$!% that use 3/4 instead of 1 :) )
  8. jerryrwm

    jerryrwm LawnSite Bronze Member
    Posts: 1,274

    1/2" for the terminal laterals up to about 5 gpm, then 1" for the rest of the zone to the valve keeping zones around 15 gpm. Only one bushing to stock, a 437-130 1x1/2 SpS bushing.

    On larger systems use 1/2", 1" and 11/2". We don't see the need for 3/4" and 11/4" as usually the amount of footage used in those two sizes is too small to justify stocking the fittings and the time to hunt up the right fitting.

    As for the 3/4" systems - that usually screams plumber install and it's usually sch 40, but they'll try to water the whole front yard on two zones and wonder why they have dry spots.

    Jerry R

    AVERDEROSA LawnSite Member
    Posts: 17

    Thanks for all your replies. I only have one hose bib so I cant open more than one. I have about 35' from my main to my home looks to be run in 3/4 cooper. My home is old built in the 1800's. I was also thinking it could be corroded. Is there a way to check for this. It just so happens that my water company is in the process of relining the main in my neighborhood. They will be running a temporary secondary service for a while. This will give a chance to replace the pipe with no down time. I would be able to take my sweet old time. OK all you pros give me your expertise. THANKS EVERYONE
  10. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 47,697

    If 65 psi is the pressure you measure while at the same time running 6 gpm, it follows that there will be more gpm at a lower pressure. If it happens that its your static pressure, you aren't going to get that 13 gpm anyway, not at a pressure that will do you any good. (what is the static pressure?) Don't worry too much about a corroded copper supply line. It doesn't date that far back. How big a property is this? A 35 foot supply main implies a smaller lot. Since reliable rotors can work with as little as 1 gpm, you can get by with what you have.

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