Another weird one

Discussion in 'Irrigation' started by DanaMac, Jun 12, 2011.

  1. DanaMac

    DanaMac LawnSite Fanatic
    Posts: 13,156

    I haven't been to this site this year, it's one that my #1 tech goes to. So hopefully I can convey the message right. We have worked on it for many years now. Older part of town, system is on very high pressure - 140 psi, 1" supply line. We are having problems with one zone. This particular zone is the only zone with rotors, all others are spray heads. I believe it has 10 RB 5004s on the zone.

    When the zone turns on, there is a quick surge, and the turrets get up, but then they won't go any higher. Usually, I would say this is from bad wiper seals, or too many heads on the zone and the zone would be stretched. BUT - if he forces the heads up, the zone is absolutely crankin'. Full resistance on the heads when he tries to push them down.

    Here are the things he has tried. He has nozzled it down to 10 GPM, and nozzled up to 20 GPM. Still the same thing either way. If he closes the ball valve at the PVB, turns on the zone, and slowly opens the ball valve, the zone comes up fine. But it won't come up with the quick turn on of a zone valve. He replaced the top of the DV with a flow control to see if he could get it to work with this slow opening situation. Still no after throttling down the valve.

    Do you think it could somehow be the high pressure? What if he put in a regulator for that zone (or at the PVB)? I will have him check pressure with his pitot tube and gauge this week. My other thought, is that since it is in an older part of town with big trees, maybe a root is starting to restrict it, and combined with the blow-by of the wiper seals at the initial turn on, there isn't enough flow to push the heads up. But that doesn't make sense when they come up by slowly turning open the BV. Any other thoughts?
     
  2. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 46,867

    why is it that Rainbird DV valves are so often mentioned in these mystery scenarios? :)
     
  3. DanaMac

    DanaMac LawnSite Fanatic
    Posts: 13,156

    Once again, higher percentage of them out there. At least for here.

    Which brings me to another point recently. Lots of failures and warranty items this year on brand new stuff. DV valves not closing, 2400 valves not closing, brand new Irritrol solenoids won't work (the new ones without the little button on top). Ewing said they have gotten both Hunter and WM valves back this year. I've turned in a bunch of 5004 heads as well.
     
  4. Irri-Light

    Irri-Light LawnSite Member
    Posts: 53

    It seems pressure is an issue. The diaphragm port can only allow so much water through it. Since the top of the diaphragm has a bigger surface area than the bottom, more water and pressure hold the diaphragm closed. When he uses the PVB to control flow it actually allows the water to move through the ports without excessive force on the top of the diaphragm. Those are my first thoughts on this.

    Will the valve open with the manual bleed? Bleeding to atmosphere would release the pressure on top of the diaphragm.
     
  5. DanaMac

    DanaMac LawnSite Fanatic
    Posts: 13,156

    Doesn't matter if it is from the bleed screw, electric through the solenoid, or manual turn of the solenoid.
     
  6. AI Inc

    AI Inc LawnSite Fanatic
    Posts: 25,207

    does RB make a 0 nozzle, ( like the blank on a hunter low angle rack? If so, try putting 3-4 in and see what happens.
     
  7. Irri-Light

    Irri-Light LawnSite Member
    Posts: 53

    Interesting.

    After it's open, does it close normally?
     
  8. Sprinkus

    Sprinkus LawnSite Silver Member
    Posts: 2,072

    I'd definitely put in a PRV with that kind of pressure on the system.
     
  9. I guess I would find an easy spot to repair the lateral and before it tees off cut it and see if it does it with an open lateral pipe. Assuming this is poly It sounds to me like it is crimping/uncrimping somewhere.
     
  10. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 46,867

    What failures are showing on these new "smooth-top" Irritrol solenoids?
     

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