Solenoid function on a irrigation valve?

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by pmaru77, Apr 13, 2009.

  1. pmaru77

    pmaru77 New Member

    Messages:
    35
    Location:
    California
    Well, while I'm trying to repair/fix my valve leaking problem, I thought I'd ask how a solenoid valve drop the pressure on one side of the diaphram valve so that the diaphram opens to let flow to the sprinklers. I am assuming that there is more pressure on the top of the diaphram when shut, thus shut. So, does the soleniod (retracting type) drop that pressure somehow?
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,013
    Location:
    New England
    A solenoid valve is an electrical device...apply power, and it moves a piston. that piston might be attached to a valve or any one of many devices. Sometimes that piston has a spring to return it to 'neutral', and some require reversing the polarity of the field, or a second actuator.
  3. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    Sprinkler valve are pilot operated. When the solenoid is off, an internal port allows mains pressure to be applied to the top of the diaphragm. A small spring adds to this pressure, whereas the underside of the diaphragm only sees mains pressure, so the diaphragm remains closed. When the solenoid is activated, it opens a port which bleeds mains pressure from the top of the diaphragm into the outlet pipe. This bleeds faster than the inlet bleed, and thus mains pressure on the underside lifts the diaphragm.
  4. Thatguy

    Thatguy Homeowner

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  5. pmaru77

    pmaru77 New Member

    Messages:
    35
    Location:
    California
    Very good......thanks. So the diaphram does have water on both sides as I thought. Also to add, the line pressure has more surface area to push on the top of the diaphram, thus more pressure downward. I think the spring keeps everyone(diaphram) in place and order while adding a little pressure. I still have not figured out why this 75 dollar valve is passing water. I cut it out for now and end capped the line temperarily.
  6. pmaru77

    pmaru77 New Member

    Messages:
    35
    Location:
    California
  7. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego

    Good point. Hydraulics is all about pounds PER SQUARE INCH
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