I have a 10 year old well water pressure tank that is losing pressure. I first noticed that my pump was short cycling. It started cutting on and off every few seconds. I drained the pressure tank and re-filled it with air to 38psi. Every thing stays fine for about two days and then the pump starts to short cycle again. I am assuming that the pressure tank has gone bad and I need to replace it. Is there anyway of testing the tank or could there be another cause to the loss of air pressure in the tank?

When pump starts short cycling, press the needle of the air input valve, if you get water instead of air you have a ruptured bladder. The air is not leaking out, it is being absorbed by the water under pressure. The bladder prevents that from occurring. You pressurized to 38#, I assume that your pump switch is set to come on at 40# and go off at 60#.

When pressurizing tank it should be done with the tank empty of all water.

Great advice by Harold! If you shut your pump off and the pressure gauge falls then I would suspect the foot check valve. Determine where your valve is located and have it checked. Good luck, Tom