How much water should be in a bladder or diapham tank. My tank is 20 gallon and has 18 psi onmmynwelol

Are u having a problem or is this just a point of info?

The pressure in the bladder tank should be 2 psi lower than the low turn on for your well pump. The turn off is usually 20 psi higher then low turn on.

As far as I can see, the manufacturer would determine amount of water in the tank by the location of bladder. With the psi as a control.

The tank will probably hold more water as the tank ages. Like a balloon, the bladder/diaphragm will expand easier after a time.

Chuck

Giddyup, you posted this question earlier. Read the answers from that post.