Pressure switch cycling rapidly at cut in

Discussion in 'Pumps and Tanks Well Forum & Blog' started by SWMICH, Jan 6, 2009.


    SWMICH New Member

    History: Water line was struck in yard causing well to discharge completely. Repaired, restarted and several days later began losing house pressure. A well driller friend of the family heard my daughter complain about her showers and showed up to fix the problem. He adjusted the pressure switch way up and added air to the tank. Pressure reduced again days later but this time I bypassed the water softener and the pressure was fantastic. (Well problems released rust sediment and clogged the Mediaguard filter in the softener.)

    Present: The pressure switch began cycling rapidly at cut-in shaking the plumbing furiously until it settled in to cut-out. After some research I discovered the air pressure needed to be 2# under cut-in setting. Made the correction (too much air pressure) and cycling had stopped...until today. Now it cycles two or three times before settling in. I replaced the pressure switch and it still does it. I did like the increased water pressure so I set the cut in back at 65# where the well guy had set it. I have now tried dropping the pressure a bit with no help.

    Observing the pressure gauge I notice just as the gauge arrives at cut-in their is a quick drop in pressure. Followed by the switch cycling and so on. The pump used to run for forty seconds to fill the tank but now fill time is much shorter. Maybe 10 seconds. By increasing the pressure have I displaced so much water from the tank that it is now undersized? Or is their a problem with the tank. The submersible pump has always moved vast amounts of water. Tank age is probably more than 15 years old. My last thought as I send this off is that each time I get the switch to stop cycling it later reappears - taking longer and longer to settle down. I think I answered my own question...believing the well tank is degrading daily. Can someone confirm or deny my suspicions?
  2. Cass

    Cass Plumber

    Sounds like when your friend pumped up the tank pressure he may have burst the need someone who can diagnose the problem and fix the bladder tank water logged???

    Maybe call the friend back and have him fix the problem again...

    SWMICH New Member

    If it is waterlogged, it isn't completely waterlogged yet. Their is some pump run time. When I said the switch was cycling I meant that rather than cutting in with a single switch closing the contacts repeatedly open and close before finally seating for pump run.

    I think the troubling part was each time I would adjust the air in the tank to coincide with the cut-in pressure I could get it to stop but over a day or so it would start again. If a tank can be partially waterlogged that might explain why its erratic or intermittent.
  4. Gary Slusser

    Gary Slusser That's all folks!

    Yes it can be a broken bladder with a small leak and the tank above the bladder won't be full of water. Drain the tank, check the air pressure against what you set it at the last time and rick the tank to see if it's heavy and if you can hear water sloshing around it in. If so you need a new tank.

    You want a small tank and a CSV or, a tank that will allow the pump to stay off for 60 seconds or more from cut out to cut in at the pressure switch settings you want to operate at.
  5. valveman

    valveman Moderator Staff Member

    Lubbock, Texas
    I think your bladder is busted and over time, more water gets on top of the bladder and increases the pre-charge pressure. Like Gary said, check your pre-charge pressure again. That pressure will not increase by itself. If the pressure is higher than you left it last time, the bladder is busted. That being said, your tank was too small to start with. You should get a minimum of 1 minute of run time to fill the tank. 40 seconds means your tank is too small.

    However, big pressure tanks are the old way of doing things. Constant pressure systems with very small pressure tanks are becoming the norm. A Cycle Stop Valve gives you the run time required and eliminates cycling, so big pressure tanks are no longer needed. Cycling is what destroyed the bladder in your tank, and you should be aware that you pump has cycled enough to also be on it's last leg as well.

    Attached Files:


    SWMICH New Member

    Thank you gentlemen, I appreciate your experience. I'll investigate the change to the constant pressure system. The tank was due to fail. The pump is long overdue but still serving us well. (pun intended...)

    Side question...

    I knowingly built a barn near the well head effectively barring a derrick truck access. With 12' walls and a distance of 6 or 7 feet from the sidewall would there be any hope of building a davit off the barn side to pull the pump for replacement? (Wishful thinking...)
  7. WV Hillbilly

    WV Hillbilly New Member

    How deep is your well & what kind of pipe is your pump hung on ?

    SWMICH New Member

    It is a 4" well, probably 30 years old and it is not plastic. I suppose that means it would be cast iron but truth be known I don't know. When I bought the house I seem to remember 150' being discussed.
  9. hj

    hj Moderator & Master Plumber Staff Member

    Cave Creek, Arizona
    Tank pressure

    The tank is an accumulator storing the water until it is needed. IF the air pressure is zero, there is nothing to push the water out of the tank. If the pressure is higher than the pump shutoff point, there is no way that water can enter the tank. When either of these happen the pump will start instantneously when you open a faucet and either run continuously or turn on and off rapidly, depending on the pump's capacity and the flow from the faucet. If the air pressure is somewhere between the pump's turn on and turn off points, then you will get some flow from the tank, but at the pressure point where the air pushes all the stored water out of the tank until the pressure in the system continues to drop to the turn on point, usually a second or so, your flow from the faucet will stop. Between zero pressure and the cut in point, the pump will push water into the tank until the air is compressed to the same pressure as that on the water side. The lower the air pressure, the more water in the tank, but the less volume of air to push it out. That is why the air pressure in the tank should be equal to the cut in point, because that will give the maximum volume without causing the lack of water just before the pump starts. But since mechanical devices can be less than accurate, the air pressure is actually set just below the cut in point as a "fudge factor".
  10. Gary Slusser

    Gary Slusser That's all folks!

    The air is set at 1-2 psi less than the cut in setting of the switch so you don't run out of water before the pump comes on and delivers more.
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