Knowing when your pressure tank is bad is a very good thing to know when your home is on a well. The pressure tank serves as a water storage tank for the water the well pump sends up to your home. This allows the well pump to remain off for a longer period of time between cycles. With any electric motor frequent starts are detrimental to a long service life. Each start uses a current up to 150% of the current used to run the motor, which builds heat in the windings of the motor. The symptom of a pressure tank, which is bad or, not precharged properly is the well pump will turn on with virtually every use of water and may cycle on and off several times a minute while using the water. If this problem is not corrected the pump will burn out in very little time bringing with it an expensive repair bill.
Pressure tanks for wells come in two types one of which has a rubber bladder separating the water from the air and is relatively problem free unless the bladder fails and the other, which has no bladder separating the water from the air. The bladder type is easily recognized by its having an air valve on the top of the tank similar to the one on a tire, while the type without the bladder has a galvanized tank with a block mounted on the side called an air volume control which has the air valve mounted on it. For the purposes of this article we are going to focus on bladder type tanks with the galvanized non-bladder type tanks being a failure when the tank rusts through or you get tired of the frequent maintenance. If a non-bladder tank fails I recommend upgrading to a bladder tank.
Testing for a failed bladder tank is very simple. All you have to do is press the pin in the center of the air valve and if water comes out of the air valve the bladder has failed and the tank requires replacement. To properly set the air pre-charge on a bladder tank you have to know the pressure at which the well pump turns on. The pressure switches on a well pump are typically 20/40, 30/50, or 40/60 switches with the low number being the pressure the pump turns on at and the high number 20-psi higher where the pump turns off at. You need to watch the pressure gauge to see what the pressure is where your pump turns on. The pre-charge pressure for your bladder tank is 2-psi less than the pressure where the pump turns on. If a pump turns on at 20 the pre-charge pressure is 18-psi or, if the pressure has been adjusted differently say turn on at 25-psi for example the pre-charge would be 23-psi. To set the pre-charge you will need a tire pressure gauge and an air pump. Turn off the well pump and open a cold faucet as low in the house as possible waiting until the water stops coming out. Many times there is a drain valve right at the tank you can connect a garden hose to allowing the tank drain down. Once the water stops coming out check the air pressure at the air valve and it should read 2-psi less than the cut in pressure where the pump turns on. If the pressure reads low pump air into the bladder until you reach the proper pre-charge pressure then close the drain valve or faucet and turn the pump back on. The well pump system should stop short cycling and have a long period of time where the tank provides the water and a longer run cycle where the tank is filling.
Another thing you may be interested in that can help prolong the service life of your well pump is installing a Cycle Stop Valve or, CSV which will allow your pump to run constantly through a prolonged water usage preventing the pump from cycling too many times shortening the life of the motor. A motor that runs constantly is a much better choice than cycling too many times per hour and with a CSV the pressure will remain constant.