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Swamp at the end of the line...

Discussion in 'Irrigation' started by jeffinsgf, Jul 24, 2005.

  1. jeffinsgf

    jeffinsgf LawnSite Senior Member
    Posts: 641

    I recently designed and installed an irrigation system on nearly 3/4 of an acre. We live in the Ozarks and the lawn slopes downhill at what is considered around here "a mild grade". The limestone bedrock is very close to the surface in many areas of the yard.

    I followed all the guidelines I could find on designing the system, and for the most part, I am thrilled with the results. However, I have one problem area. One section of the yard is a large ovoid with the narrow end surrounded by a driveway on both sides. This is at the bottom of the slope and water naturally drains to the area. I planted a "rain garden" (feet wet plants) at the bottom even before the irrigation system was contemplated. I have three lines running down the hill, each a separate zone. The heads are 36 to 40 feet apart and I am running Hunter PGP's. I have great head to head coverage, but now the lower end is turning into a swamp. I am establishing new zoysia from seed in the area, so I am trying to keep the lawn moist everywhere. But when the top of the slope is thoroughly dry, the bottom is still swampy. I have reduced the nozzle size on all the downhill sprayers and cut the arc down on the middle bottom so that it does not cover the worst of the area. I think the worst of the problem is coming not from the system when it is running, but when it shuts off. When the valves close everything in the line drains out of the bottom sprayer. On the advise of my seed supplier, I am watering 3 times a day for a short duration, but that means that the swamp is getting 3 times as much line drainage as it normally would...or 6 times as much if you consider every other day as the "norm".

    Is there something I could add to the valves that would prevent the line from draining? Or should I not worry about it, since the three drains a day will only be for a couple of weeks? Any other thoughts or ideas? Thanks in advance for any insights you can offer.
  2. AceSprinkleRx

    AceSprinkleRx LawnSite Member
    from Wyoming
    Posts: 95

    How long and what size are the three zone lines running downhill? How far apart are they from each other? Do you have any idea of how much water is getting pooled up at the bottom of your slope? I used to live in SE Kansas and also had a cabin south of you close to Kimberling so I'm familiar with the terrain.

    You mention you designed the system yourself, did you factor in precipitation and absorbtion rates?

  3. jerryrwm

    jerryrwm LawnSite Bronze Member
    Posts: 1,274

    First step would be to get the PGP check valve model. Or change the low heads to I-20s with a check valve. These check valves under the head will hold up to 10' of elevation so hopefully you are not exceeding that. If you are, it means that the line will continue to drain until the check valve spring exceeds the water head pressure.

  4. jeffinsgf

    jeffinsgf LawnSite Senior Member
    Posts: 641

    The East zone is 140 feet from valve to last head. The first 40 feet are 1" Class 200 PVC and the balance is 3/4" Class 200. The Central zone is 200 feet, with the first 60 feet 1". The West zone is 200 feet with 100 feet of 1". They run fairly parallel 40 feet apart. At the point where the ovoid narrows, the central zone doglegs and has the last spot on what would appear to be the West zone.

    Did I consider precipitation and absorbtion rates? No. I laid everything out for head to head coverage, which I thought was as much consideration as was needed. Now I am discovering that the 90 degree heads are putting out twice as much water on their area as the 180's and 4 times as much as the 360's. Hunter's PGP's have salvaged that problem, since their variety of tips supplied will allow you to decrease the precip without killing your radius. Absorbtion rate would be a nightmare to try to quantify on this lot, since the soil type changes every few feet. The currently swampy area is a very rocky (limestone) loam. 100 feet upslope it is sandy clay full of igneous rocks and sandstone.
  5. jeffinsgf

    jeffinsgf LawnSite Senior Member
    Posts: 641

    Thanks, Jerry. I took a look at Hunter's website. They also offer a check valve to install into normal PGP's that will hold back 2 feet. The last head in each line is probably at least 20 feet below the valve, but if I add the field install kits to each head in the line, it would greatly reduce --- though not eliminate the amount of water draining. The alternative would be to dig up and replace the lower two units I guess.
  6. jerryrwm

    jerryrwm LawnSite Bronze Member
    Posts: 1,274

    Nozzle selection will not totally correct the standing water problem. It will help it by reducing the applied water in some areas. As you have found out, the 90° nozzle needs to supply 1/2 the GPM of the 180° nozzle which needs to supply 1/2 the GPM of the 360° nozzle. This will make the precipitation rate more equal over the area.

    The low-head drainage will not be changed by changing nozzles however. The volume of water draining out of the pipe remains constant every time the system is run. Even if you go from 4.0 gpm nozzles to 2.0 gpm nozzles the amount of water in the pipe doesn't change. Installing check valves either in the heads or even in the lateral or directly under the head will help solve the drainage problem.

  7. Dirty Water

    Dirty Water LawnSite Fanatic
    Posts: 6,799

    Where is Bryan to come in here and tell you to water for shorter amounts of time, with delays between zones, several times a day?
  8. jerryrwm

    jerryrwm LawnSite Bronze Member
    Posts: 1,274

    Just read your post and went and found this information.

    PVC Adjustable Spring Check Valves
    PVC Adjustable Check Valve
    Series 1205 FIPT x FIPT PVC Adjustable Check Valve

    Series 1235 FIPT x MIPT

    Use to restrain head pressure in elevated irrigation lines.
    Ideal for preventing syphoning in slope and nursery irrigation

    * Male or female threaded connection
    * Iron Pipe sizes ½" to 1½"
    * 200 PSI static pressure rating @ 72ºF
    * Adjustable from 5 lbs. to 15 lbs. spring tension
    * EPDM seal

    In addition to the standard features of Flo's Check Valve, this is adjustable, providing 5lbs to 15 lbs spring tension to retain a column of water 12 to 36 foot head.


    One or more of these on the line and you could have the problem whipped.

  9. jerryrwm

    jerryrwm LawnSite Bronze Member
    Posts: 1,274

    HaHaHa....Jon - you ain't right!! LOL God'll get you for that!

  10. jeffinsgf

    jeffinsgf LawnSite Senior Member
    Posts: 641

    Thanks for your help, Jerry. I understand that changing tips isn't going to help the drainage problem -- which is, I think, the only problem I have. I was watching the swamp grow and changing tips to minimize the water before I saw that the real culprit was line drainage. I am going to go check out the line check valves you linked right now.

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