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Thread: help with impact sprinkler performance

  1. #1

    Default help with impact sprinkler performance

    I bought a house last summer and am having trouble with the back lawn irrigation system. There is a circle lawn with about a 48.5' diameter. There are 5 perimeter Toro impact sprinkers evenly spaced around 3/4 of the lawn and the last 1/4 has four spray heads. There is also an impact sprinkler about dead center in the lawn.

    All of these are on the same valve and the radius reduction screw has been used in each of the rotors. Last summer the ground around the head in the low part of the lawn became just saturated mud. I dug up the head expected to find a broken line but found no such problem. Just toro funnypipe running off 18" at which point i stopped digging since the ground was getting dryer in that direction.

    This spring the grass for the first two feet around the rotors is bright green and the rest of the lawn that the rotors cover is browning up. When they run the enclosure is filled with water and it spills out like an overfull cup. Is that normal for an impact rotor?

    I've been educating myself over on irrigationtutorials.com and it looks like at the least i need to replace the valves in the rotors to insure uniform application, remove the radius reduction screw from the stream and i'll probably cap 3 of the spray heads and replace the fourth with another impact.

    So, assuming i'm on the right track, any advice on why the impact rotors are spilling so much water and the lawn is only green right next to the heads? Note I'm not getting the 'donut' that is described in some pages, just the bright green saturated ground within a couple of feet and medium to little coverage elsewhere.But maybe it is the same cause, low pressure? All i know about the rate of flow is the valve is 1" and at least the last couple of feet to the head is 1/2" funnypipe. The water company says our standing pressure is about 45psi.

    The kids want to play on a green lawn, any and all advice appreciated.

    -Wandering_burr

  2. #2

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    You have a break either in the pipe or the head or both. Just had the same problem last week with one of mine, problem was both the pipe and the head.

    Check the funny pipes fittings.

    The cup will fill up, but if it is flowing out, it is time to replace.

  3. #3
    DIY Senior Member rdtompki's Avatar
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    You also might consider changing to Hunter rotors or similar. These types of sprinklers are much more uniform than impact sprinklers in my experience. I've had -25 and -41 models installed for almost 15 years without any problems.

    Rick

  4. #4
    Plumber jimbo's Avatar
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    Rotors, impact heads, and fixed spray heads should not be mixed on the same timere zone, as they have different precipitation rates and therefor require different timing.

  5. #5

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    Thanks for the advice. Since i posted i noticed that two of the impact heads are RainBirds and the others Toro. At this point i want to replace all the heads and end up with 6 Rotor heads on the exterior of the lawn and one in the middle. This should give me head to head coverage. Since the impacts are connected with 1/2" funnypipe and i only need a throw of about 25' I was looking at the Hunter PGJ rotors. Later I discovered the MP Rotator product which will also throw water 25' without a problem and should have more uniform coverage although at a slower rate. Any suggestions on which would be a better way to go?

  6. #6
    Sprinkler Guy Wet_Boots's Avatar
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    Stick with impact heads, and use Maxipaws, or prepare to have difficulties with poor performance with gear-drive rotor heads. Your 45 psi static pressure kind of paints you into a corner. Nothing you can buy will cover as effectively at low pressures as a Maxipaw impact head will.

    How is this system plumbed? Is there a backflow preventer? Your location? (relates to backflow prevention requirements)
    Last edited by Wet_Boots; 05-22-2008 at 10:33 AM. Reason: questions

  7. #7

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    The only equipment that is visible are six 1" valves. If there is a backflow preventer it is buried somewhere.

    I'm in San Diego and the house is about 9 years old.

    The impacts are mixed brands and haven't been maintained so i'll dig up the ones that have the bright green circles around them and dead zones 3-12 feet away and replace the funny pipe and connections to eliminate any leaks. I'll also standardize on the MaxiPaw. It pains me to do all that work and not 'upgrade' to rotors but if the water company says we have 45PSI and not even MP Rotators will have enough pressure to work right it sounds like that is what i'll need to do.

    I just hope i don't find more than 3-4' of funnypipe at each head. If I do, i'll come back here for more advice....

  8. #8
    Sprinkler Guy Wet_Boots's Avatar
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    Funny pipe length isn't so much of an issue. In California, on flat ground, you should be using antisiphon zone valves to get your backflow prevention, if you want to preserve your water pressure. They have to be located a foot higher than the highest head they feed.

  9. #9
    In the Trades Gary Swart's Avatar
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    There may be something I don't understand (yeah, a lot I don't understand, I know) but I don't know why you would need anti siphon valves on each zone. A double check back flow preventer can be install below ground level although it should be in a box for access, and will suffice for the entire system. That said, all back flow devices should be inspected by a certified inspector annually. In my city, it is mandated and enforced. I just had mine tested and the inspector found the check valves were worn to the point they were not completely preventing the back flow. Total cost of the inspection including repair: $50

  10. #10
    Sprinkler Guy Wet_Boots's Avatar
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    Quote Originally Posted by Gary Swart View Post
    There may be something I don't understand (yeah, a lot I don't understand, I know) but I don't know why you would need anti siphon valves on each zone. A double check back flow preventer can be install below ground level although it should be in a box for access, and will suffice for the entire system. That said, all back flow devices should be inspected by a certified inspector annually. In my city, it is mandated and enforced. I just had mine tested and the inspector found the check valves were worn to the point they were not completely preventing the back flow. Total cost of the inspection including repair: $50
    Double Check Valve Assembly = not allowed in California, as well as not being allowed in many other states that follow a regional code. The reason is simple, since a DCVA is not rated to protect against toxic backflow. Other forms of backflow protection are, including the RPZ and PVB, and the humble antisiphon zone valves. The ASV has an atmospheric vacuum breaker built into it, and since the AVB has to be downstream of any valve, that's why each zone valve is an ASV. Using ASVs will keep pressure losses to a minimum.

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