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Irrigation Blowouts, PSI and Back Flow Preventers.

Discussion in 'Irrigation' started by White Gardens, Sep 22, 2012.

  1. White Gardens

    White Gardens LawnSite Fanatic
    Messages: 6,776

    Picked up three accounts this year that have irrigation systems.

    We take care of the maintenance on the systems, and really it's been fairly simple with no issues through the season besides a bad install on one property and a few fittings that have come loose.

    It's about blow-out time though. I plan on getting a 90cfm pull behind compressor to do the job right.

    Couple of questions though (and yes a search but just found a bunch of babble in each thread ;) ).

    1.) What would be the minimum PSI? I know you shouldn't go over 80, but that's probably way more than needed for most systems. That and I suspect on one system I deal with that the install was on the cheap side, so I don't want to blow out the un-clamped barbed fittings at the heads.

    2.) One property has a back-flow preventor out-side. I know your not supposed to blow through a BFP, so is just cracking the valve slightly after the blow-out enough to keep from having any freeze damage with the water in the pipe leading to the BFP? Or should I try to at least drain the BFP if possible.

    3.) Also, thought I know this is a loaded and probably un-answerable question, how much time do you have after the water is blown out before you could possibly do damage due to no water and air friction. I don't have a remote and don't feel the need to purchase one just for 3 blow-outs. I do have an employee, but he is deaf and relaying messages with a walkie-talkie wouldn't work and so I would have to run back to change the zones myself.

    I appreciate the help. These systems are simple enough and for just three systems it's a nice little learning experience. One being 4 zones with a booster, one being 9 zones with a booster and one being a 9 zone residential. And yes, I know to cut the power to the booster. :)

  2. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Messages: 50,569

    * crickets *
  3. White Gardens

    White Gardens LawnSite Fanatic
    Messages: 6,776

    Crickets, no, shouldn't be any in the system.

    I'm hoping it's too soon for that comment..... [​IMG]

    Last edited: Sep 22, 2012
  4. CAPT Stream Rotar

    CAPT Stream Rotar LawnSite Fanatic
    Messages: 6,192

    Well its more volume and PSI together.

    You can use a 5 gallon air compressor @ 150 psi and be doing nothing..

    Blow through the PVB all you want the world will not end..

    but expect to change some internal parts in the future.

    Just start off light with the air my friend, maybe half open ball valve.. Look @ or go to the heads, step on one..if you can easily step on lets say the last one you might want to put a little more air through it...Don't be scared

    There is a very friendly guy on here named Mike Leary that welcomes new comers and their questions...

    Remember to shut off the ball valve @ the POC or turn breaker off.

    good luck.
  5. DanaMac

    DanaMac LawnSite Fanatic
    Messages: 13,219

    Oh yes, quite welcoming. He will hold your hand all the way, with patience and encouragement. :laugh:
  6. White Gardens

    White Gardens LawnSite Fanatic
    Messages: 6,776

    Don't plan on blowing through the PVB. I'm just concerned as it is about 10 feet out-side the building and I know there will still be some water left in that pipe when done. Seems kinda like a bad location if you ask me, but I'm no install professional.

    And thanks. I figure 90cfm will be sufficient and will probably start out in the 30psi range to be on the safe side. I've fixed three different heads this season do to the poly coming away from the barbed fittings from either soil movement or tree roots. That's what has got me concerned about the PSI on this system.

    Now, I haven't found a ball valve for one of the boosters :hammerhead:, but have found it to be plugged in with a standard three prong outlet. So the plan is to just un-plug it as the controller is plugged into the same place.

    One of the boosters I haven't discovered the power-supply for yet. It's in a stock room and they've piled mounds of crap in that area, so I'll have to do some digging.

  7. White Gardens

    White Gardens LawnSite Fanatic
    Messages: 6,776

    And, there is no PVB for the irrigation system specifically for one of the systems. I wondering if they assumed the large PVB for the entire facility was good enough. :nono:

  8. DanaMac

    DanaMac LawnSite Fanatic
    Messages: 13,219

    1. - no clear cut answer for this. There is a balance between PSI and CFM. Hopefully you have an adjustable PRV so you can play around with it. Each site may need different PSI.

    2. - blow through the BFV all you want. Not the best practice, but we ado it all the time.

    3. - it's a learning thing. You may need to blow out each zone 2-3 times, shorter amounts each time, to get a feel for when enough is enough. Blow out the zone to where no water is coming out of the last head, then come back to it again after the other zones. See how much water is actually coming out a second time. There may be depressions in the pipe or dead end sections that may hold water.

    Good luck, happy learning.
  9. White Gardens

    White Gardens LawnSite Fanatic
    Messages: 6,776

    Thanks, good to know that you can blow through the PVB, just sucks that I didn't install the system, so I don't know the quality of the installs.

    I do plan on doing each zone at least twice for the reasons you stated.

  10. 1idejim

    1idejim LawnSite Fanatic
    Messages: 11,316

    I have seen some of WG's work on the other forums, he's no hack so give him a break.
    Posted via Mobile Device

    sorry dana, was slower than you were fast. send the summit pics
    Last edited: Sep 22, 2012

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