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what is wrong here?? any ideas???

Discussion in 'Irrigation' started by jonspolaris, Jul 13, 2001.

  1. jonspolaris

    jonspolaris LawnSite Member
    Posts: 130

    My mom lives in a condo subdivision, its on 4.5 acres. All the grass area is irrigated. The contractor that installed the irrigation used hunter PGP heads. Each head covers a good size area. The main feeding the system is 2” in diameter and is city water. The problem is that there are MANY large brown areas that arnt getting watered, and the system runs for 20 minutes each day. In these areas the grass is very dry. Some zones have 30 (yes 30) sprinkler heads on them. I think the problem is that there are too many heads and not enough water coming out of each head. Some of the heads look like a little kid peeing, they just don’t have much volume.

    Am I correct?? Any ideas?? thanks
  2. racerdave

    racerdave LawnSite Senior Member
    Posts: 260

    jonspolaris, I think you are on to something there.

    You need the gpm requirements for the heads, and also know the pressure and flow of the supply water to determine how many heads per zone you can run.

    Plus you need to know the pipe sizing for figuring frictional piping loss also.

    when on city water you also have to take pressure fluxuations into account. In other words if a bunch of your neighbors are also trying to water at the same time you are, then you will have a much lower pressure to work with.
    good luck
  3. jonspolaris

    jonspolaris LawnSite Member
    Posts: 130

    thanks dave,

    i think the heads put out 6-8 gpm, but im not positive. The zone accross the street from us works great, they have VERY good flow. On that zone there is 14 heads, down the street there is another zone with 30 heads covers a VERY big area. the 2" main is about 650' long and is the same diameter the whole length.
    I think the zones at the end of the street are getting the"short end of the stick" in terms of pressure. i think the pressure at the meter is about 50psi.

  4. Currier

    Currier LawnSite Senior Member
    Posts: 564

    Is there any way to switch out the nozzles and reduce the volume of water gpm needed? The zones would have to run longer but maybe there would be enough pressure to at least get the place watered.
  5. EarthWorks

    EarthWorks LawnSite Member
    Posts: 135

    What is the spacing between heads. May be able to nozzle down and still get good coverage. 50 psi sounds low for a system like that.
  6. Louis

    Louis LawnSite Member
    from Atlanta
    Posts: 15

    Check the head spacing and make sure that you have head to head coverage-meaning that each rotor hits the next closest rotor with the end of its stream.That may be why you have the rainbow dry area effect.Most manufacturers spec the heads for 50 psi up to 70psi.If you have that many heads you need to split the zones to have enough flow and they can do a good job at 3gpm nozzles unless thsy are full circle then they need to be 6gpm.Hope this helps.
  7. John DiMartino

    John DiMartino LawnSite Silver Member
    Posts: 2,555

    The Hunters have screens in the bottom,when mine plug up partially,they spray weak,ID check the system pressure in the pipe,and clean the screens on a few heads,see if they have algae buildup or rust/scale build up first.
  8. Avery

    Avery LawnSite Bronze Member
    Posts: 1,389

    Like John said..check your screens. If that is not it you probably need to drop the gpm inserts in the heads. 6-8 gpm is huge for that type of system. Audit your system and see what type of coverage you are getting. Put some rain gauges out, run the system and see how much water it is putting down in a cycle.
  9. jonspolaris

    jonspolaris LawnSite Member
    Posts: 130

    thanks Guys,

    How do i check the screens in the heads???

    i was watching a zone today and it was pathetic. the heads just shot out a stream that landed in a small area, it dident blast out of the heads. The coverage isnt that good becaues there are many backyards with brownspots from being dry. It hasent rained in 2 weeks here. Most of these zones u can see that the lawn is green where the stream lands and then brown in the middle.

    i would guess there 20-25ft apart in spacing. i still think the problem is to many heads on at one time.

    the system is running for 40 min a day ( 2-20min cycles) and there is still brown spots. i just think there isnt the quanity of water going on the lawns that is needed.

    does anybody know how much water u can get out of a 2" water line hooked up to the city water line?? we are very close to the water tower, and presser is good here.

  10. Chuck Sinclair

    Chuck Sinclair LawnSite Senior Member
    Posts: 336

    Bottom line is you are correct you can NOT have 30 PGP rotors on one 2" valve with 50 psi at the meter. even if you change the nozzels its not going to make a differance.:blob3:

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