I have a diaphragm well tank that keeps kicking on and off pretty fast when using the water in the house. I have check the pressure when pump is off and the pressure is 38psi and the gauge reads 40psi and 18psi when pump turns on at 20psi. This has me worried because it just started about a month ago but seams worse now. For example, toilet is flushed and the pump kicks on and off ten times before the toilet tank is filled.

The short-cycling you are experiencing is the ultimate sign. You can also press the air valve at the top for a few seconds. If water comes out, then you have your answer. You can also use a hammer to lightly "ping" up the side of the tank. You can hear a change in the sound of the pinging when you reach the top of the water in the tank. Should be about halfway up. Yours will likely be nearer the top.

You can do a temporary fix. Turn off the system and drain pressure down to zero by opening a faucet. Use an air compressor to put ten or fifteen pounds of pressure in the tank. That will hold for several weeks, long enough for you to replace the tank.

The short-cycling you are experiencing is the ultimate sign. You can also press the air valve at the top for a few seconds. If water comes out, then you have your answer. You can also use a hammer to lightly "ping" up the side of the tank. You can hear a change in the sound of the pinging when you reach the top of the water in the tank. Should be about halfway up. Yours will likely be nearer the top.

You can do a temporary fix. Turn off the system and drain pressure down to zero by opening a faucet. Use an air compressor to put ten or fifteen pounds of pressure in the tank. That will hold for several weeks, long enough for you to replace the tank.

I thank you for these tips and had a quick squirt of cold water in my face this morning checking the air valve tip out. (haha) Well now I can replace the tank with a little bigger one. Again thanks.

Wise decision. Best wishes.