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junk123 · Feb 26, 2008, 03:26 PM

Hi Folks,

I noticed my domestic pump controller "short cycling". I drained the pressure tank and noted that the air pressure was 10 psi when empty (Well-Rite 240-04, bladder type, approx 13 yrs old). Should this pressure be 40 PSI at empty?

When refilled, the pressure is 40 psi. But, when I watch the water pressure upon filling, it goes up to 40 PSI and then I can audibly hear a hissing/water bubbling sound and note that the water pressure surges to 60 PSI and the well controller shuts off the pump... but the water pressure immediately drops to 42... then normal use brings it down to 40 PSI and it short cycles again...

Is this indicative of a broken pump? water line that lets in air? Or something more sinister? Any ideas... at this point, I'm going to lower the cycling pressures to get a better pressure differential. ( BTW... I hear the sound in my pressure tank ). And I'm going to keep on looking on the net... (could it simply be that I need to pressurize the tank to 40 psi before filling?)... thanks for any help offered... ken

hkstroud · Feb 26, 2008, 03:57 PM

Don't know much about bladder tanks but I would suspect a leaking bladder. It is my understanding that the pressure on the empty bladder tank should be 2 lbs below the pump cut in pressure.

jlisenbe · Feb 26, 2008, 04:10 PM

HK is correct. When the tank is empty, the pressure above the bladder (should be an air valve at the top of the tank) should be set to, in your case, 38#. When you refill the tank, even if the bladder is bad, the tank will actually work OK for several weeks or even months until most of the air above the water dissolves into the water. Then you end up with a tank full of water... waterlogged.

If the system continues to short cycle, then you probably need a new tank. The deal is this. It will only short cycle when you are using water. As long as you're not using water, it should sit there for days and not come on. If it is short-cycling when not in use, then you are probably looking at a bad checkvalve.

junk123 · Feb 27, 2008, 11:19 AM

Hi Folks again... I went on the 'net and found that my tank has a diaphram. It was apparent that it was at full extension and subject to "system hydraulic locking" as the diaphram would quickly reach maximum expansion, causing the up pressure surge and unusual sounds as the pump flow was stopped, perhaps for 1/2 second (until the pump controller kicked off the pump). I drained the system, pressurized the tank and noted normal cycling and operation. I also noted that tapping on the tank, which previously indicated it to be about half full... now sounds like there is no water level present. I expect to monitor the system over time to see if in fact the pressure tank has failed. Thanks for your comments. Ken

hkstroud · Feb 27, 2008, 01:54 PM

Does that mean you fixed it?

jlisenbe · Feb 27, 2008, 04:09 PM

It is normal to have the tank be mainly empty when you refill it. This is because the area under the bladder is full of air as is the area above the bladder. After several months, the air below the bladder will dissolve into the water and you will notice the tank water being at a more normal level.

mountaindweller · Mar 28, 2012, 12:54 PM

What is meant by short-cycling?

speedball1 · Mar 28, 2012, 01:12 PM

Hi mountineweller and Welcome to The Plumbing Page. At AskMeHelpDesk.com. You're responding to a 4 year old dead thread Look in then upper left hand corner of the first post for the date before you post, Thanks,
When a pump short cycles it turns on every time you draw a glass of water or flush a toilet. This is usually caused by a lack of air cushion in the bladder or pressure tank. In a bladder tank this is caused by a faulty membrane. Does this answer your question? Regards, Tom