Shallow Well Lawn Irragation pump cycle problem

Discussion in 'Irrigation / Sprinkler Forum' started by lfmgtc59, Mar 12, 2011.

  1. valveman

    valveman Cary Austin Staff Member

    Joined:
    Mar 15, 2006
    Occupation:
    Pump Controls Technician
    Location:
    Lubbock, Texas
    Even though it is 8’ from the check valve down to the water level, it should stay full of water. The check valves act like putting your finger on top of a straw full of water. The water can’t get out until you remove your finger and let air in. 9 checks valves leave 9 places to fail. With the power off, if any of these checks leak back, you are going to lose prime. With the power on, the pump should come on and refill the pressure tank, after the water in the tank leaks back through the bad check. So if you leave the power on, the pump will cycle on and off while no water is being used.

    Worn check valves always close differently. One time it may seal pretty good. The next time it may not seat in the same place and won’t seal at all. One or all of your check valves is leaking back. The process of elimination maybe the only way to find it.
     
  2. lfmgtc59

    lfmgtc59 New Member

    Joined:
    Mar 12, 2011
    Location:
    Clearwater FL
    Thank you Valveman... that makes a lot of sense.

    Its a real bummer about the check valves though... I just installed new ones.

    I did notice when flushing the lines that I'm getting some crud... less now I've done it a few times. So it is quite possible something gets stuck in the seal causing it to fail to seal.

    So far this is what the pressure over the last 24 hrs looks like - the pump has not kicked on:

    1 - 36 psi
    2 - 36 psi
    3 - 35 psi
    4 - 35 psi
    5 - 35 psi
    6 - 35 psi
    7 - 35 psi
    8 - 35 psi
    9 - 35 psi
    10 - 34 psi
    11 - 34 psi
    12 - 34 psi
    13 - 34 psi
    14 - 34 psi
    15
    16
    17
    18 - 34 psi
    19 - 33 psi (6:30)
    20
    21 - 32 psi (8:30)
    22
    23
    24 - 34 psi (11:30)


    I think the move down from 34 - 32 and back up was caused by cooling and heating (about 20 degree difference in ambient temp, plus sun exposure) as the pipes are exposed at this time.

    I appreciate all the assistance!

    Thank You

    Lee
     
  3. valveman

    valveman Cary Austin Staff Member

    Joined:
    Mar 15, 2006
    Occupation:
    Pump Controls Technician
    Location:
    Lubbock, Texas
    That many check valves and pumping crud, I would get a low pressure cut-off switch (FSG2M4). PITA to prime with but, will save your pump if you lose prime.
     
  4. lfmgtc59

    lfmgtc59 New Member

    Joined:
    Mar 12, 2011
    Location:
    Clearwater FL
    Valveman:

    Would this do the job?

    20/40 Psi Pressure Switch
    Brand: Square D
    Model: FSG2J20M4
    SKU: 303904

    20/40 PSI Standard Pressure Switch With Low Pressure Cutoff, 1/4" - 18 NPSF Internal Thread Opening, Low Pressure Setting At 20 PSI, For Electrically Driven Water Pumps.

    An integrated unit would be easier to plumb in at this point.

    Thank You

    Lee

    P.S. Pressure still holding at 34
     
  5. valveman

    valveman Cary Austin Staff Member

    Joined:
    Mar 15, 2006
    Occupation:
    Pump Controls Technician
    Location:
    Lubbock, Texas
    Yep, that is the one I am talking about.
     
  6. lfmgtc59

    lfmgtc59 New Member

    Joined:
    Mar 12, 2011
    Location:
    Clearwater FL
    Lowes and Ace do not carry them, so I ordered it from drillspot.com. It will be about a week or so, so until then I'll cut the breaker and deal with it, as I cannot risk burning out the pump..

    At what psi does the low pressure cut out activate?

    Thanks Again

    Lee
     
  7. LLigetfa

    LLigetfa DIYer, not in the trades

    Joined:
    Feb 6, 2011
    Occupation:
    Semi-Retired
    Location:
    NW Ontario, Canada
    Approx 10 PSI
     
  8. lfmgtc59

    lfmgtc59 New Member

    Joined:
    Mar 12, 2011
    Location:
    Clearwater FL
    Good Morning valveman / LLigetfa

    OK... the system has been working more or less - had to fix another couple of cracked pipes on the sprinkler head side of the valves and my pressure switch has some issues (it does not want to kick on until somewhere between 5 & 15 depending on the day and sometimes does not want to shut off at 40), but that will be fixed as soon as he replacement arrives today. However, there is another rather puzzling issue:

    The sprinkler system runs through its cycle, the last zone up runs about 30 psi. It closes and the pump builds up to around 39, then begins to lose pressure in spurts. It starts going through this sort of 5+/-lb pressure "surge" (you can hear what sounds like water like shooting into the tank at each surge) but after each surge it drops to a lower pressure. This levels off around 20 / 25 and if I don't intervene just stays there running. It has happened twice.


    The first time I cut the breaker, shut the valves to the well point side of the pump and the sprinkler valve side of the system, thus isolating the pump and tank. Since I was going to put on a better gauge I decided to do it then. To my surprise only compressed air came out when I removed the valve. very little water.

    The second time it happened, I switched one of the zones back on... within a couple of minutes it was running 30 psi and running the system just fine, when the zone shut off, the system gradually built pressure to 40 and switched off as normal.

    Ok... its done it again. I followed the same approach as above in the second time with the same result.

    I at first thought I had bled the well dry, but as in the second time around I was pumping 30psi out to the spinklers when I opened the zone valve... I suspect that is not the case...

    Any ideas?

    Thank You

    Lee
     
    Last edited: Mar 22, 2011
  9. valveman

    valveman Cary Austin Staff Member

    Joined:
    Mar 15, 2006
    Occupation:
    Pump Controls Technician
    Location:
    Lubbock, Texas
    You have a leak in one of the suction lines. When you are pumping full flow to the sprinklers the air leak doesn’t amount to much. But when the sprinklers are off and you are filling the pressure tank, the flow rate gets so low that it is easier to draw in air from the leak than water from below. You can find a leak with shaving cream. It will make a hole in the shaving cream where it sucks in air. Or you can rap the connections with plastic rap. When you rap the connection with the leak, the surging will go away.
     
  10. lfmgtc59

    lfmgtc59 New Member

    Joined:
    Mar 12, 2011
    Location:
    Clearwater FL
    Much appreciated valveman... it must be a very slow leak indeed...

    Fortunatly the way the system is set up once the problem occurs I can shut off the two main lines leading to the well points individually. That way I can tell right away if it is a leak above or below grade and if below which way...

    Hopefully it is above grade as I just filled all that in and seeded last weekend... Anyway the info on the shaving creme and plastic rap is appreciated.

    I suppose where ever the leak is will mean cutting it all apart again... as it is in suction any chance in putting something on the leak and it getting sucked in and sealing??

    Again, Thanks for the advice.

    Lee
     
  11. valveman

    valveman Cary Austin Staff Member

    Joined:
    Mar 15, 2006
    Occupation:
    Pump Controls Technician
    Location:
    Lubbock, Texas
    If the leak is in a threaded joint then no. If the leak is in a glue fitting, then let it suck in some more glue. Sometimes it works.
     
  12. lfmgtc59

    lfmgtc59 New Member

    Joined:
    Mar 12, 2011
    Location:
    Clearwater FL
    I did find a small leak (very small) at the PVC to Iron threaded joint at the pump. The thread on the pump is not the best, but it is all I have, so I laid the heavy duty pink Teflon tape to the joint and have had no leaks since…

    However… (does this ever end??)

    Now it may run through the 9 zones 4 or 5 times over a two day period without a hitch, but for no apparent reason pull a bunch of air on the 5th or 6th time through and get hung around 15 – 25 psi and thus not shut off.

    The following all occur regularly:

    1. Runs through all 9 zones with no perceivable issues at all.

    2. Sometimes, perhaps midway through a full nine zone cycle (it differs from run to run) all of a sudden a mass of air hits the pump (I am able to tell by the sound, but also visually at the clear filter I installed). In mid cycle the system seems to handle this with no apparent problem.

    3. Sometimes, at the end of a full nine zone cycle all of a sudden a mass of air hits the pump (I am able to tell by the sound, but also visually at the clear filter I installed). Because the flow has been shut off as the cycle is over, this appears to cause some type of cavitation, which seems to allow the pump to not drop below 10 psi (low pressure cut off), while not allowing the pressure to build above 25 psi.

    Thus the system just runs and runs, builds up heat, eventually creates steam (did this once), but at any rate just keeps running and running.

    If I open any of the sprinkler valves and give the system a flow, in about 2 – 3 minutes it is making pressure and working fine. Then nine times out of ten once the valve shuts the system builds to 40 psi and shuts off, and hold about 35psi.

    My guess is something is leaking in one of the well points below the check valve???

    Also getting very fine sand in the filter…

    Any ideas?

    Thank You

    Lee
     
  13. valveman

    valveman Cary Austin Staff Member

    Joined:
    Mar 15, 2006
    Occupation:
    Pump Controls Technician
    Location:
    Lubbock, Texas
    I think you are right, and that could also cause the sand.
     
  14. lfmgtc59

    lfmgtc59 New Member

    Joined:
    Mar 12, 2011
    Location:
    Clearwater FL
    This does not sound good...

    With nine well points, is there any tricks of the trade that might help isolate which one is the problem?

    Thank You

    Lee
     
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