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Thread: Shallow Well Lawn Irragation pump cycle problem

  1. #16
    DIY Junior Member lfmgtc59's Avatar
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    Default Update - So Far So Good...

    Hey Guys

    Ok here is the outcome...

    I couldn't find a bladderless tank, so I went with the bladder tank. Because of size and mounting restrictions in my application I went with the 7 gallon tank as the next largest was 20 gallon and to large to fit.

    I pre-charged the tank at 18psi. I fully primed the system back to the wellpoints using a couple of valves at the end of the lines I put in for that purpose. At the same time I pre-charged the output side to the spinkler valves.

    It took just 2 minutes to get up to pressure once I turned the pump on and started the system and the valves started opening.

    The system held a nice even pressure through the 9 zones around 30psi. When the last zone finished the pressure gradually climbed to 40, the pump shut off and there was a sudden pressure drop, but only to 36psi where it stopped rock solid.

    I have turned the breakers off for the night (did not want to take a chance with the pump). I will see tomorrow if the pressure has held overnight. It has held 40psi overnight before, so I can't see there would be a problem. If so I will flip the breakers and start the system manually in the morning.

    I guess that will be the real test to see if it all fires up tomorrow.

    I REALLY APPRECIATE ALL THE HELP!!!

    I'm pretty sharp on researching most of this stuff, but what is in the books isn't always exactly what you find in the field - as you guys probably know - so it really helps to have someone who has been there done that letting you know where you've gone wrong.

    Thanks Again... I'll let you know how it comes out tomorow.

    Lee

    Lee

  2. #17
    DIY Junior Member lfmgtc59's Avatar
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    Ok this morning the pressure was at 0 psi. Because I had switched the breaker off, I don't know if the pump would have kicked on at 20 psi and been able to re-pressurize the system or not.

    As there are no leaks in the pipes, joints etc. the only thing I can think of is leaks through the check valves back into the well points.

    I had to re-prime the system, and even at that it took 15 - 20 minutes to build enough pressure to properly work the sprinkler system. You could hear at the sprinkler valve that there was a lot of air being pushed through the line. My thought is that there are 9 well points and the water is 8' below surface, so there is a lot of air to move before the pump really can get up to normal operating pressure / volume.

    Is that a valid assumption?

    After that, all seemed to go well (no pun intended). I ran it through an abbreviated sprinkler schedule and when the cycle ended the pump built up to 40 psi and cut off as it was supposed to. Pressure stabilized at 36 psi again.

    Leak down by the hour has been as follows:

    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 -
    11 -
    12 –

    Based on the 0 psi this morning, this is rather unexpected. The pump has not kicked on at all, so the pressure has been steady. I'm going to monitor for another few hours and see what happens.

    So what should I see happen if the system is functioning the way it should?

    Thank You

    Lee

  3. #18
    DIYer, not in the trades LLigetfa's Avatar
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    There must be more than one leak. If it were just leaking back to the wells, the pipe would not fill with air. Somewhere air has to be leaking into the system.

  4. #19
    DIY Junior Member lfmgtc59's Avatar
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    Default

    clarification:

    "leak down by the hour" may be misleading - these were the actual pressure readings by the hour... actual leak down was only 2 psi over a 10 hour period


    I have all the horizontal pipes and the first foot or so below the check valves on the well points fully exposed and I cannot find any evidence of a leak even when pressurized to 40 psi over a several hour period.

    Not trying to be argumentative, just trying to fully understand... But since the water in the well points is 8' below ground level, wouldn't that mean that there is an 8' column of air in the well point vertical pipes when the system is at rest?

    Also, I cannot understand why over 12 hours yesterday I lost 36 psi and so far over 10 hours today I only lost 2 psi...


    Thank You
    Last edited by lfmgtc59; 03-13-2011 at 07:46 PM.

  5. #20
    DIY Junior Member lfmgtc59's Avatar
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    Its now been 21 hours and I have lost 4 psi... course the temperature at the start was 75 and now is 56... which could account for some pressure loss as the pipes, pump, and tank are exposed. Its supposed to climb to 80 today, so I will find out.

    What should I expect to happen here? Should the system hold pressure indefinitly - in theory I would think so, but in reality what would you say should happen?


    Thank You

    Lee

  6. #21
    Moderator valveman's Avatar
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    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.

  7. #22
    DIY Junior Member lfmgtc59's Avatar
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    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

  8. #23
    Moderator valveman's Avatar
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    Quote Originally Posted by lfmgtc59 View Post
    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.
    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.

  9. #24
    DIY Junior Member lfmgtc59's Avatar
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    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

  10. #25
    Moderator valveman's Avatar
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    Yep, that is the one I am talking about.

  11. #26
    DIY Junior Member lfmgtc59's Avatar
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    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

  12. #27
    DIYer, not in the trades LLigetfa's Avatar
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    Quote Originally Posted by lfmgtc59 View Post
    At what psi does the low pressure cut out activate?
    Approx 10 PSI

  13. #28
    DIY Junior Member lfmgtc59's Avatar
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    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 by lfmgtc59; 03-22-2011 at 05:25 AM. Reason: update

  14. #29
    Moderator valveman's Avatar
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    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.

  15. #30
    DIY Junior Member lfmgtc59's Avatar
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    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

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