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What is a "water-logged" tank on a private water system and what causes it?
All private water systems using a well, whether equipped with above ground or submersible pumps, have some type of pressurized water storage tank in the plumbing network. There are two types of storage tanks, those with bladders inside and those that do not have bladders. The bladder is just a flexible container within the metal tank that is filled with water but contains no air itself except what is dissolved in the water. The purpose of a bladder is to separate water from the air column in the tank. However, both bladder and bladderless tanks have an air column above the water in the tank. To properly function within a set pressure range (30 to 50 psi is common), this air column is essential. If a bladder leaks or splits inside the tank, the tank will still function just like a bladderless tank. The air column tends to dissipates over time, especially in bladderless tanks, as the tank is filled to a certain water capacity and air capacity over and over. When the air volume gets low, the tank fills almost completely full of water. This is called a water-logged tank. The sign of a water-logged tank is the pump kicking on and off in a matter of seconds as the water is being used, with pressure reading going up and down very fast. The minimum cycle time on a pump should be one minute before it kicks on and off during water use. To fix a water-logged tank, you must shut off the pump, drain the tank, shut off valves to make the tank air tight, and then add air back to the tank. On bladderless tanks, and probably some tanks with bladders, there is an air valve on top of the tank to do this. After emptying the tank, you will need a tire pressure gauge. Add air to give a pressure reading that is 2 psi below the low kick-on pressure for the pump. For example, if the system is set to kick on at 30 psi and kick off at 50 psi, fill the empty tank with air until you get a pressure of 28 psi. Then turn the pump back on. If you have problems with this operation, call a specialist. There are other FAQs in this database on how private water systems function.



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This website was developed by the ACES Water Quality Team, under the leadership of Dr. James E. Hairston. It is funded, in part, by USDA-CSREES water quality grant support under Section 406 of the Agricultural Research, Extension and Education Reform Act of 1998.