Need Advice

Discussion in 'Irrigation' started by coxlandscaping, Jan 9, 2008.

  1. coxlandscaping

    coxlandscaping LawnSite Member
    Posts: 104

    I have an irrigation system to install in a new subdivision I had the water dept. to come out and give me a psi and gpm test at the meter. It was 140 psi and 39 gpm they did remove the meter when they tested it so I don’t know how much you would lose thru the meter? The meter size is 5/8. I normally use a zurn Wilkins 975xl 1” backflow and here we use pvc pipe I use schedule 40 at the backflow and psi 200 for the rest of the runs or zones. My question is do I need to install a pressure reducer and if so should it be installed on the downward side of the backflow and what would I be losing as far as gpm?
  2. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 47,709

    You don't lose gpm, you lose pressure (different amounts at different flow rates) ~ a 5/8 inch meter may not be rated for more than 20 gpm, so planning for more isn't advisable (although most modern 5/8 meters can allow more flow) - I would probably put the reducer upstream of the RPZ, and use something like a Wilkins BR-4, which has an output range to 150 psi. There are additional pressure losses in a PRV, beyond the pressure regulation.
  3. hoskm01

    hoskm01 LawnSite Fanatic
    Posts: 5,690

    If you want more flow, can you pay the city more for a bigger meter? Do you need more?

    You definetly need to reduce the pressure; agreed that it should be upstream from the RPZ. Remember that you will lose more pressure through your lines and to the head, so plan accordingly. Not too much, not too little is the goal. Valves in the heads work well also.
  4. AI Inc

    AI Inc LawnSite Fanatic
    Posts: 25,392

    You can always use a flow control master valve. I use these quite a lot in areas with extremly high pressure.
  5. coxlandscaping

    coxlandscaping LawnSite Member
    Posts: 104

    I don’t really need any more flow my biggest concern is too much pressure I don’t want to damage any pipe or heads we use primarily Hunter. I haven’t tried using a master valve before on any system that we have installed because up to this point most of the system have been marginal at best on psi and gpm.
  6. irrig8r

    irrig8r LawnSite Platinum Member
    Posts: 4,535

    I agree with Wet Boots. I use a lot of Wilkins BR-4s in situations like yours. I highly recommend them for their adjustability.
  7. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 47,709

    Allow for pressures to drop as the years pass, and more homes are tapping into the supply.
  8. Mike Leary

    Mike Leary LawnSite Fanatic
    Posts: 21,978

    Excellent point, but unless one is tite with the developer, you have no clue
    what the eventual psi will be. Best one could do is check with the puryeyors
    & see if they spec a minimum & design for it. I've been burned by this,
    once...not pretty.:hammerhead:

  9. Mdirrigation

    Mdirrigation LawnSite Silver Member
    Posts: 2,639

    Depends where you make your tap , will the house have a pressure reducer , if the connection is at the house tie in before the reducer and have one installed for the system itself. I design systems in this area to work off of 65 per cent of the available pressure and flow if the estimate is given early spring or late fall when water use is low. ( I have one area in the winter they have 75 psi and 30 gpm , mid summer it drops to 35 psi and 10 gpm) . State in your contract that the system was designed to operate with a minimum of xxxx Psi and a minmum of xxxx gpm . And that drops in pressure and flow are not your responsibility. As far as a master valve we use them on every system we install .

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