Diagnos this problem

Discussion in 'Irrigation' started by EagleLandscape, Sep 26, 2007.

  1. EagleLandscape

    EagleLandscape LawnSite Platinum Member
    Male, from Garland, Texas
    Posts: 4,347

    Ok, so I was looking at a repair earlier tonight.

    Problem: LOW/NO WATER PRESSURE AT THE VALVES.

    Customer has raindial control and they have 6 stations.

    Water meter is at the curb, and the backflow T's in up by the house. Unfortunately the BF is underneath mature indian hawthorne and carissa holly shrubs.

    I opened the manual bleed valve (rainbird dv series) and barely anything trickled out. extremely low pressure. Also tried running manual station from the controller, it opens up, but very low pressure. Just bubbles if anything from the heads. This happens at all six stations, so I know its not a solenoid or diaphragm issue.

    I did not have a pressure gauge with me, ( i know i know) but we manage a large house across the street, and this block has great pressure.

    Coming out of the backflow is like 1 1/4 black (poly?). Sub division is about 16 years old.

    there is not a wire in the wiring bundle at the controller for a master valve. The water meter is not spinning, so that eliminates a possible mainline leak.

    UNless there is a MV, but just not a wire?

    I did find a large underground hole right after the BF where it looks like there was a break in the pipe and it eroded out tons of soil. But if there was a break, the meter would still be spinning. The only way to find out what this hole leads to, is to dig up all of the mature bushes. (last option I want to mess with.)

    Only thing I could think of is that there might be a gate valve right after the backflow? But heck if I know where to find it.

    I'm confused? What else could be the issue?

    No pressure at valves, but no leak and no master valve?
     
  2. wolfpacklawn

    wolfpacklawn LawnSite Member
    Posts: 120

    We don't use poly tubing for main lines around here but I have seen 1/2" poly get crimped off by roots.

    I would check the pressure right after the backflow valve. If good pressure there then obviously the problem lies somewhere between the backflow and the valves.

    Are all the valves in the same location?

    Is there possibly a filter on the main line before the valves?"

    Obviously that hole sound suspect.

    It may be easier to run a new line to the valves than root up mature trees and bushes.
     
  3. WalkGood

    WalkGood LawnSite Bronze Member
    Posts: 1,910

    I figure this system used to work, right?

    Water pressure inside the house is good?

    Any garden hose bibb spigots to check the pressure?

    Is the irrigation feed pipe totally from outside the house or is the a plumbing tap inside for the irrigation? If so check to see if someone has turned down the feed valve.

    I once had a low flow problem on the irrigation at a customer where it had been fine prior. Inside the house, all faucets worked fine. After checking everything outside, they finally let me in the basement to check the ball valve for the irrigation.

    As they both hubby n wife stated, that valve was full open. But the whole house water main gate valve was cranked down big time. Seems they had shut it off to fix a faucet, didnt turn it back open all the way. Faucets seemed fine since they were all low-flow anyway.

    Happy hunting!
     
  4. You checked to make sure the meter is open all the way? If it is from what you've posted getting to that DCVA seems like the only best next option.
     
  5. bobw

    bobw LawnSite Senior Member
    Posts: 807

    Do you suppose that when they repaired the leak at the BF, they let some large rocks into the line and that those are hung up in the pipe blocking your flow?
     
  6. Kiril

    Kiril LawnSite Fanatic
    Posts: 18,298

    Funny you should mention this. I went out on a no flow call last week and found the 1/2 poly had been pinched, not by a root directly, but by a staple that had been pulled down by a root. It had completely pinched off the line.
     
  7. turfnh2oman

    turfnh2oman LawnSite Member
    Posts: 127

    Start from scratch. Go to the source or closest point [preferably at meter side of backflow] and check pressure. Next check pressure at mainline side of backflow. If that all checks out okay then proceed downstream [mainline]. Sounds like you have a valve somewhere in the mainline [probably closer to backflow] and probably that previous hole you don't want to dig up will reveal at least something. Meter won't spin if leak is after main valve until it opens and a zone is on. Only other option is a restriction in the line somewhere especially if all zone valves are acting the same.
     
  8. Mike Leary

    Mike Leary LawnSite Fanatic
    Posts: 21,762

    I'd look at the DCVA..a check spring may have broken or the check itself
    may have stuck closed.....do your purveyors not spec yearly testing on
    backflow assemblies?
     
  9. PurpHaze

    PurpHaze LawnSite Fanatic
    Posts: 5,496

    I personally love sitches like this as it brings out the detective skills. Sounds to me that there's a problem at/near the backflow device. You'll need to check GPM/PSI before/after it to further chase the problem.

    Oh... and one more thing... examine the sitch a little more closely with an open mind. Often we run into situations where it's a combination of problems. Don't go in with a narrow mind thinking it's only one problem or you run the risk of missing something.
     
  10. EagleLandscape

    EagleLandscape LawnSite Platinum Member
    Male, from Garland, Texas
    Posts: 4,347

    I need to take pressure reading off of hose bib. thats for sure.
    my gauge was in my other truck when i went to check out the issue.

    I would love to just dig up the mainline between the dcva and the first valve but it goes under a 15' driveway and through 10year shrubs.

    we'll see.
     

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