Diagnosis
The storage tank bladder has likely lost its pre-charge air pressure, or the shut-off valve (ASO valve) isn’t working right, stopping production too early.
How to Fix It
First, check the tank pressure. Shut off the feed water, open the faucet to drain the tank completely, and close the faucet. Use a standard tire pressure gauge on the Schrader valve (looks like a tire valve) on the tank. It should read around 7-8 PSI when empty. If it’s at 0 or very low, use a bicycle pump or small compressor to bring it back to 7-8 PSI. Then turn the water back on and let it refill. You should hear the system shut off with a click when full.
If That Didn't Work
The Automatic Shut-Off (ASO) valve might be stuck or failing. This is the black rectangular valve with four tubing ports. If it’s stuck open, you’ll hear constant draining. If it’s stuck closed, production stops prematurely. Tapping it gently can sometimes free it, but it usually needs replacement.
Heads Up
When checking the tank pressure, make sure the tank is COMPLETELY empty of water. Any water left in it will give you a false high reading. It has to be dry.