Question about Amtrol ST-12-C THERM-X-TROL ASME Expansion Tank, 5 Gallon

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Hank I thought my pressure switch was also bad. but I am on my second new one

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  • eeawk May 19, 2009

    I redraind the new tank to reset pressure to 28Lbs. I put 45LBS into the tank to get read of all water and air if any was trapped. While waiting my gauge would climb to 10 - 15 Lbs while everything was shut down and off. No loss to tank pressure at all so it was not leaking.
    I then released the pressure in the tank to 28Lbs left the house out of the system. I then refiled the the tank with water at the 28Lbs turned on the water to drain and the have the pressure switch do its thing.
    It would drop to 29 Lbs and restart, but every now and then the pump would shut down at 30 Lbs and the contacts would stay contacted. it would stay off for a minuet then resart on its own?
    the pressure would drop to 0 and when it shut down. the house pressure would not go above 34Lbs.. I would attempted to adjust the larger screw for more cut off pressure but it would not do anything for me. I would have to put 35Lbs of air in the tank inorder to have any pressure in the house at all. no instructions one the smaller screw what is that for?

  • HANK MCNEIL May 11, 2010

    Please re-describe the symptoms and what happens - dosen't make sense.

    Note: comment on this listing instead of creating a new one so we have our past conversations before us please.



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Just a suggestion but your pump could be clogged in the ground, just by readind you are on well system? the contacts are together because they are trying to pull water to get up to the proper amount of water pressure. that is why they contact then overheat release then contact again, how old is the pump????

Posted on May 30, 2009


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The check valve will stop over-expansion from pushing pressure back into the supply line.
The real question is what is causing the pressure.
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Water pump cycles to often. When pump turns on, pressure gauge shoots up to 50 lbs right away without pumping much water.

Sounds like a well fed system with a pressure tank that has lost its air charge. Check for a water tank with a tire pressure type stem fitting, should also have a pressure gauge. Most newer tanks have a rubber diaphram inside to keep the air and water from mixing, but a lot of older ones don't and the newer ones will develope a leak that will produce the simpoms you describe. Try adding a few pounds of air pressure to the top of the tank and check for leaks. Warning: Compressed air can escape explosivly if the tank is badly rusted out but if your water pressure goes to 50# without the tank leaking, it should be safe to add up to 25# of air. The air charges the water system and allows the pump to shut off until enough water is used to lower the pressure back to set points on the control switch. It's not a good idea to adjust the set points on the switch unless all parts in the system have been checked for safety to the new pressures.

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