low pressure problem

Discussion in 'Irrigation' started by justgeorge, Jun 24, 2005.

  1. justgeorge

    justgeorge LawnSite Senior Member
    Posts: 352

    I'm working on a system that someone else installed last fall and has never worked well. Hooking up my pressure gauge to a outdoor faucet I only get 40-50 psi. In my own home (same neighborhood) I get 90psi at the faucet. I tried turning in the screw on the pressure reducer in the basement but when I turn it in very far it starts hissing like there is probably a toilet leaking from the higher pressure. Homeowner wasn't home so I couldn't go checking all the toilets.

    I'm thinking I have the homeowner isolate the toilet with the weak valve then turn up the pressure and then they fix that toilet valve.

    After I can get some higher pressure I'll have to go back and put bigger nozzles in all the PGP heads; whoever installed this tried to compensate for the low pressure by using #3 nozzles (< 1 GPM).

    Anyone else come across a similar problem?

  2. Mdirrigation

    Mdirrigation LawnSite Silver Member
    Posts: 2,642

    Clean the screen in the pressure regulator , or install the sprinkler supply prior to the regulator , We never turn up regulators due to the fact that some houses have plastic lines to the sinks and toilets , and the rubber hoses to the washing machines.
  3. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 47,722

    Second that leaving the regulator alone, except for that cleaning. Teeing off for the system prior to the regulator will give you extra pressure for thr sprinklers.
  4. Critical Care

    Critical Care LawnSite Bronze Member
    Posts: 1,654

    Well, the #3 nozzle at 40 psi is 1 gpm. I wonder how many of these PGPs are on a zone, and if the zones are maxed out on their flow rates? Perhaps even staying at 40 or 50 psi you could bump up to some larger nozzles for better coverage.
  5. drmiller100

    drmiller100 LawnSite Senior Member
    Posts: 562

    i wish all my account had 40 psi consistently.

    sounds like there is a feed problem ot the house. how many gallons per minute do you get at 40 psi????
  6. justgeorge

    justgeorge LawnSite Senior Member
    Posts: 352

    There are 5 PGPs on each zone. The flow gauge was reading 10-11 gpm, which should support bigger nozzles. When I swapped them over on one zone I'm only getting 15-25 feet spray. With #2 nozzles on each head I get longer spray but VERY poor coverage; it's all at the end of the spray.

    Thanks for the input on moving the tap-in before the pressure regulator.

  7. jerryrwm

    jerryrwm LawnSite Bronze Member
    Posts: 1,274

    I'm thinking that you may have pressure loss problems due to improper pipe sizing also. You can operate a system on 40-50 psi if the piping is correct.

    Also is there an elevation change where these heads are considerably higher than the meter?

    As was previously stated, check the PRV and clean the screens.

    Another problem could be a kinked line between the curb stop and the house.

    Good Hunting.
  8. justgeorge

    justgeorge LawnSite Senior Member
    Posts: 352

    The pipe is 1" PVC up to the valve boxes, which are all located in the landscape bed next to the house within 10' of the backflow. Coming out of the valve boxes it switches to 1" poly and they run in a bundle together under the sidewalk then separate to run out to all the zones. I can't be certain that they used 1" throughout the system, but it is 1" leaving the valve box. I was checking yesterday for a kinked line between the backflow and the first valve, but that's when I found they used PVC up to the valves so that ruled out the kinked line.

    There is an elevation change, maybe 8' or so, on some of the zones farther out, but the problem affects even the first zone next to the sidewalk.
  9. bicmudpuppy

    bicmudpuppy LawnSite Silver Member
    Posts: 2,781

    To say this sounds repetitive, but check the house supply. The possibility that the kink is in the copper going into the house. Inside or outside meter? Did you check the meter to make sure it was fully open? Sounds like a no-brainer question, but I've caught myself forgeting upon occasion to check the obvious. If the plumber had the water off for some reason and didn't open it back up fully............. Also check the house shutoff. Is it a ball or gate valve? If it is a gate valve, are you sure it is opening fully? Just some things to check in the obvious category.
    And the backflow is? and are you sure there isn't a restriction within it? Stuck/fowled check? etc.
  10. Critical Care

    Critical Care LawnSite Bronze Member
    Posts: 1,654

    If there were some obstruction in the service line, then likely you would not be getting that flow reading of 10 to 11 gpm, but I'm still trying to visualize this problem.

    With 10 to 11 gpm and a pressure of 40 psi, you should be able to stick #3 nozzles in all five of those PGPs and have things work. All I can figure is that you're losing your flow somewhere downstream of where you said that you were getting that 10 - 11 gpm.

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