Sprinklers spraying way too far.

Discussion in 'Irrigation / Sprinkler Forum' started by stars1234, Sep 29, 2006.

  1. stars1234

    stars1234 New Member

    Sep 29, 2006
    retired software test engineer; active prof. singe
    Provo Utah USA
    I had a sprinkler system installed in my front yard, about 1500 ft sq. It didn't seem to work right. I called the installer back but he wasn't willing to fix anything without charging lots more $$$.

    I had a number of bids, most were within a few hunderd dollars of each other. They were given by people who obviously had been in the business a long time.

    this fellow was young, looked like he could use the money, his bid was a couple of hundred less than the others. I decided to go with him because I he looked pretty hungry. --my mistake for trying to be nice.

    My son ot a job repairing sprinklers a month later and he was appaled at the job. He had to tear out almost every sprinkler, put in different ones, one circuit with rotors, other's with popups. As I've been trying to fix the mess, I found that laterals put down by the installer are in some places only 1 inch below ground level. There are no drains. The laterals go, up and down and change pipe diamater, willey-nilley. I asked about that and he said he was using pipe he had left over from other jobs. Before I could even make a map of the layout, he had covered over the trenches and pounded the dirt down with the bucket of a backhoe.

    Anyway, I'm pretty upset about it all. Especially since I am disabled, haven't the money to redo, can't lift mor than three pounds, and blew out my knee a couple of months ago.

    As I try to work with what my son put in, I am mistified over how to determine the pressure at the sprinkler.

    On the Rainbird pop-ups, I can turn the center screw (that's supposed to adjust the arc radius) all the way in, but it has no effect. All it does it fall through. There's no limit to the radius at all.
    On Hunter rotors, I can adjust the spray distance by using different size nozzles, but with them just put in and not having turning the screw into the water stream, they shoot about 20' further than the specs say they would at the highest pressure.

    I don't understand this.

    My son says that to determine the PSI at the sprinkler head, I divided the number of sprinklers on a valve by the pressure at the valve.

    The PSI at the valve is 110 and the gph is 14.4.

    One valve has 12 popups on it--this is the one that the center screw has no effect.

    By my sons way, 110/12 = <10 PSI per popup. (Only one circuit is on at a time).
    But the info for the popups say the pressure they work at best is 30 psi. If I have <10, then why doesn't the adjusting screw do anything?

    I went to the valve box and turned the pressure down at the valve until adjusting the screw on the sprinkler actually had an effect--this was nearly all the way off, at the valve.

    The same for the rotors. I have 4 on one circuit. That would make 110PSI/4rotors or about 27 PSI/rotor. Yet, the water stream, regardless of which nozzle is in place, shoots 50% farther than it would at maximum pressure on the largest nozzel (70 psi). So, again, I turn the pressure down at the valve (almost all the way off) to try and get close to the distance the water stream should be going, according to the specs for the nozzel that's in the rotor.

    Obviously, something is wrong. Either the manufactures specs are completely wrong or the way to calculate the PSI at the sprinkler is not as simple as dividing the PSI at the head by the # of sprinklers on a circuit.

    Can someone explain, what's going on? --trying to balance these sprinklers is just one of so many problems.

  2. Verdeboy

    Verdeboy In the Trades

    Jun 12, 2006
    All your sprinklers are pop-ups. I assume that the Rainbirds are sprayers, sometimes called "misters". Regarding these Rainbird misters, in order to lower the arc radius, they must have a plastic filter located just under the nozzle. When you turn the center screw in the nozzle, it pushes down on the filter and reduces the flow. When the filter is missing, the screw just falls through the hole. You should be able to completely shut off the flow that way.

    I hate all Hunters and Toros, and always replace them with Rainbird Maxi-paws. I can optimize the Rainbird rotors to deal with high or low water pressure, and adjust the arc and the spray in a matter of seconds.

    If you still can't get the sprinklers adjusted with your current water pressure, you can either add more sprinkler heads to your zones or install a pressure reducing valve (PRV).
    Last edited: Sep 29, 2006
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  4. jimbo

    jimbo Plumber

    Aug 31, 2004
    San Diego, CA
    You do not divide PSI by the numer of heads to come up with any meaningful number. The only way to know the dynamic pressure at a head would be to measure.

    Based on some considerable experience, I would offer that if your flow is actally about 14 GPM, then 110 PSI static at the valve is too much. Typical residential systems are often designed to run off 60 PSI at the valve, and then zoned to not exceed flow limits for that pressure and your pipe size.

    The most direct solution to your issue is to install a pressure reducing valve. Sounds like there are othere issues with the system, but this would be a start.

    Depending on what brand and model of control valve he installed, 110 PSI may be too high, and you may have premature valve failures.

    I hate to even bring up the subject of BACKFLOW? Did he install any?
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