Well/pump gurus, I need some help please

Discussion in 'Irrigation' started by bblawncare, Jun 21, 2008.

  1. bblawncare

    bblawncare LawnSite Member
    Posts: 129

    Looked at a system today. Owner says it worked fine 5-6 weeks ago. Now the sprinklers won't come up and won't change zones. When I turned the pump on, it took a minute or longer to get water to the pump and the sprinkler heads would not even pop up-water just "drooled" out.

    Its a 2 yr old Goulds GT15, sprinklers are on indexing valve (imagine that, an index valve in FL). Don't have any info on well-depth, water level, etc.

    I closed the discharge to sprinklers and did a flow test @ the hose bib on top of the pump. I got 12 gpm (we usually get 30-35 gpm from our 1.5 hp pumps on wells down here). My static pressure @ the hose bib was 30 psi. I put a vaccuum gauge on the pump and opened the hose bib-my reading was mostly between 15-20, every now and then it would get as low as 10. I opened the discharge to the sprinklers, my psi was a steady 10psi, and vaccuum gauge was fluctuated between 20 & 25. Problem is, I am not sure exactly what this info is telling me. I am thinking either an air leak between the pump and well or a low water level in the well.

    There is a 1.5" brass check valve vertically attached right where the suction line goes into the well- suction line is only about 3' to the well. This check valve was newly installed in January by another company. Lastly, the owner had sod installed 2 months ago-company used sod cutter, and installed sod right up to and around pump. Thinking maybe they hit the suction line while working causing some damage. Any thoughts or guidance on what the psi/vaccuum readings are pointing to? Many thanks...
     
  2. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 47,323

    25 feet of water is about as good as you will get before cavitation starts (sound of gravel in the pump, but it's actually air bubbles)

    How many gpm is the system designed to use?
     
  3. bblawncare

    bblawncare LawnSite Member
    Posts: 129

    I only calculated the one zone that tried to come on in the front-it was 24gpm, but I imagine the other 3 zones could vary if they are anything like our typical old systems here in FL.
     
  4. bblawncare

    bblawncare LawnSite Member
    Posts: 129

    So the degrees of mercury on the vac gauge are indicative of the height the pump is lifting the water? I did not get a tutorial on the use of a vacuum gauge-I've tried researching on the computer, but have not had much luck.
     
  5. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 47,323

    You have to convert readings. Your gauge was maybe marked in inches of mercury? (think barometer) ~ You have to make your own observations regarding cracked pipes. Air bubbles (without the cavitation noises) in the pump output could be a clue.
     
  6. Waterit

    Waterit LawnSite Silver Member
    Posts: 2,906

    BB, we deal with this all the time up here in NW Florida.

    Sounds like the pump lost its prime. Grab the outlet piping and see if you can turn it in both directions. If so, you'll have to repipe both the outlet and suction sides from the male adapters out. If you have room, put a 2" x 3" galvanized nipple in the suction side, then attach a NEW brass check valve.

    Here's how we pipe 'em up here: http://www.lawnsite.com/showpost.php?p=2348817&postcount=18

    What caused the loss of prime? Only the Shadow knows. Check the overall depth of the well and the depth to water. If depth to water more than about 12 ft., HO needs new well. We've been doing 1-2 per week this spring, as our drought continues.
     
  7. Dirty Water

    Dirty Water LawnSite Fanatic
    Posts: 6,799

    The impeller could be melted from cavitating.

    If repriming it does not work, pull the pump apart and look at the impeller, its probably plastic.
     
  8. bblawncare

    bblawncare LawnSite Member
    Posts: 129

    Is there any general rule of thumb on the vacuum gauge readings and what they may indicate. In my research I've found/read that weak readings (less than 20) point to a pump problem and high readings indicate suction line problems, and that readings 30 or beyond would be a plugged well or line. Also that if the pump is able to pull a 25 or 30 then there is nothing wrong with the pump, that the pump would not be able to pull that kind of vacuum if the impeller was damaged...I realize the water level in the well probably plays into this, but if that is known, can these different readings point one in the right direction of where the problem lies?
     
  9. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 47,323

    Do you know the water level in the well? If you were pulling 25 inches of mercury on the vacuum gauge, I'd start wondering about low water. Or a clogged point.
     
  10. AI Inc

    AI Inc LawnSite Fanatic
    Posts: 25,297

    Just curious, any chance the point is clogged?
     

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