Well System - Pressure Drops

Discussion in 'Irrigation' started by Laclu007, May 8, 2007.

  1. Laclu007

    Laclu007 LawnSite Member
    Posts: 15

    I have a system running on our home well. The main feed for the irrigation system runs off of the main pump line, just before the pressure switch/pressure tank. There are 14 zones, with from 5-8 heads on each zone. When I turn on a zone, the heads pop-up fine, with full pressure. However, after about a minute, the pressure drops down, causing some of the heads to go back down, due to lack of pressure. After about 20-30 seconds, the pressure kicks back in, and the heads spray at full pressure. The cycle then repeats itself. This happens at all times of the day, and when there is nothing else drawing water from the system.

    I'm running a Hunter ICC controler, Hunter I-20 heads, and rainbird valves. As far as I can tell, the cycle/soak is not turned on. (I'm not sure if this is what happens in that mode)

    Any ideas why this is happening and/or suggestions to fix?

    Thanks,

    Brent.
     
  2. bicmudpuppy

    bicmudpuppy LawnSite Silver Member
    Posts: 2,781

    To me, you are describing a pump cycling on and off. The pressure drops down to a point, the pump kicks on and the pressure comes back up. Pump reaches the shut off point and the pressure drops back down. Your going to burn out a pump fairly soon at that rate. If the pump isn't kicking on until the pressure is so low the heads aren't staying up, then I would say your pressure switch is out of adjustment/fouled. You can check it and adjust it, or clean it and then adjust it and your problem should go away if the system worked in the past and was designed correctly. At what a pressure switch costs, if it won't adjust "up", I would replace it and adjust the new one. If your in anyway unsure about how to adjust the pressure switch, I strongly urge you to get someone who understands pumps to make the repair. We are talking about a $25-40 retail part that is going to cost you a pump if it isn't fixed.
     
  3. Dirty Water

    Dirty Water LawnSite Fanatic
    Posts: 6,794

    Your well pump is cycling.

    What happens is that your pump is outputting more water (GPM) than your heads can use, so the pressure rises until the cutoff switch kicks the pump off.

    Then the heads use enough water to bring the cutoff switch to its lower cutoff point, and it turns the pump back on...and it repeats.

    This is very very hard on a pump, and you could damage if it you keep running it.

    If the system worked great, and only started cylcing this year, I'd suspect a bad pressure switch or a waterlogged pressure tanked over incorrect sprinkler nozzling.

    If thats the case, get a pump expert out there ASAP.

    EDIT: Beat me to the post Bryan.
     
  4. Laclu007

    Laclu007 LawnSite Member
    Posts: 15

    Thanks for the replies. I have shut off the system, and will get a pump guy out to have a look at what's going on. I do know the switch was changed a year ago.

    I'll update when I have a fix.

    Thanks.

    Brent.
     
  5. Laclu007

    Laclu007 LawnSite Member
    Posts: 15

    Just talked with a Pump guy. They are coming next week to install a Cycle Stop Valve, which will mechanically keep the pressure constant so the pump will not constantly cycle. As mentioned here in the previous posts, the hardest thing on a pump is the start/stop, not the pump running.

    As the pump guy said, the irrigation system is usually an afterthought to a well system, and is put on prior to the pressure valve/pressure tank, without any additions made to the system ton compensate or regulate the system for it's additional use for irrigation.

    I'll let you know what happens after the new valve is put in place.

    Brent.
     
  6. Dirty Water

    Dirty Water LawnSite Fanatic
    Posts: 6,794

    Seems to me that if the system was functioning correctly before, then at one point its output was properly matched to the GPM of the well pump.

    That points towards a bad switch or a water logged pressure tank, and putting a cycle stop valve on it will just hide the symptom, not fix the problem.
     
  7. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 48,035

    It might be as simple as adjusting the pressure switch. Almost every stock pressure switch gets adjusted when a sprinkler system is installed, and the reason is to avoid cycling. In some cases, a Cycle Stop Valve could prevent proper operation, if the system was operating with more than 60 psi at the tank.
     
  8. Valveman

    Valveman LawnSite Member
    Posts: 53

    A Cycle Stop Valve will not prevent "proper operation". The CSV will stop the pump from cycling an solve your problem. Let us know how it works.
     
  9. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 48,035

    If the system was running at 70 psi tank pressure before the new switch was installed, and needing every psi, there may not be anything currently manufactured that could be added between pump and sprinklers, that wouldn't degrade sprinkler performance.

    Of course, this all site-specific. An install that has a 50 psi (common recommendation from Hunter) head pressure, and an RPZ backflow preventer, will have to have a tank pressure at 65 psi or higher. Maybe a 70 psi version of the plastic CSV might be created.

    Still, I am wondering if a call to the original installer might not have resulted in a quick visit to readjust the pressure switch, to end the cycling when the sprinklers run.

    I may get some labels printed up for my well water installs, that have the pressure switch settings on them, so a replacement switch can be readjusted to continue operation without cycling.
     
  10. Valveman

    Valveman LawnSite Member
    Posts: 53

    He doesn't need every bit of pressure the pump will provide or the pump would not be cycling. I do not see where he said anything about needing 70 PSI. The 60 PSI Cycle Stop Valve with a 50/70 pressure switch setting will fix the problem. The CSV does not hide anything. It simply turns any pump into a variable flow pump. The CSV will make the output of the pump exactly match the outflow of the sprinklers. In this way there is no extra water being produced to cause the pump to cycle on and off. This is the best way to control a pump for a sprinkler system because, the sprinklers can now be designed to match the yard and not the pump.
     

Share This Page