pd600 keeps running and draining non-stop, won't shut off. the drain line has constant flow.

Diagnosis

The continuous flow of water down the drain line in the Frizzlife PD600-TAM3 indicates a failure in the Automatic Shut-Off (ASO) mechanism. In a healthy system, the ASO valve acts as a pressure-sensitive switch; once the pressure in the storage tank reaches approximately 60-70% of the incoming line pressure, the valve closes the feed water supply, stopping the RO membrane from producing more water and, consequently, stopping the waste stream. When the drain never stops, the system is essentially stuck in "production mode." This failure is typically caused by one of three things: a faulty ASO valve diaphragm that cannot seal, a leak in the storage tank's air bladder causing a drop in back-pressure, or a "stuck" check valve located at the exit of the RO membrane. If the check valve fails to hold pressure, the pressurized water from the tank leaks backward through the membrane and out the drain, preventing the ASO valve from ever sensing that the tank is full. You can confirm this by closing the tank valve; if the drain continues to run for more than 15-20 minutes after the tank is isolated, the ASO valve itself is the culprit.

How to Fix It

To resolve a stuck ASO valve or a pressure imbalance, follow these precise steps to reset the system's hydraulic pressure:

1. Close the blue tank valve (turn 90 degrees) to isolate the storage tank from the rest of the system.
2. Open the RO faucet at the sink and let the water trickle out for 30 seconds to bleed off any trapped air in the lines.
3. Close the RO faucet and observe the drain line. The drain should continue to run for 3 to 5 minutes as the membrane fills. If the drain stops on its own within 10 minutes while the tank is closed, your ASO valve is working, and the issue is actually a lost air charge in your tank.
4. If the drain continues to run indefinitely with the tank closed, locate the ASO valve (the small square component where the feed water enters). Gently tap the housing of the valve with the handle of a screwdriver to dislodge any sediment trapped in the diaphragm.
5. Turn the feed water supply valve off and then back on quickly to create a "pressure spike" that can sometimes force a stuck diaphragm to seat correctly.
6. Slowly reopen the blue tank valve and monitor the drain. It should now shut off once the tank reaches full pressure.

If That Didn't Work

• Replace the Check Valve: The check valve is the small elbow fitting located at the "pure water" exit of the RO membrane housing. If this valve leaks, water flows backward from the tank to the drain. Replace this fitting with a new one to ensure pressure is maintained against the ASO valve.
• Repressurize the Storage Tank: If the tank bladder has lost its air charge, the system will never reach the pressure threshold required to trigger the ASO valve. Use a pressure gauge to check the air valve (Schrader valve) at the bottom of the tank. It should be between 7-10 PSI when the tank is empty. Use a bicycle pump to add air if it is below 7 PSI.
• Replace the ASO Valve Assembly: If the valve is physically failed or the internal seal is torn, the entire ASO component must be replaced. Ensure you use the specific Frizzlife-compatible 4-way shut-off valve to maintain the correct flow rate and pressure sensitivity.
• Check for Kinks in the Drain Line: Ensure the black drain line is not pinched or kinked. While a kink usually slows the drain, it can create back-pressure that confuses the ASO valve's ability to shut off properly.

Heads Up

• Filter Life: A constant drain flow puts excessive wear on your pre-filters and the RO membrane. If the system has been running non-stop for more than a week, consider replacing the sediment and carbon filters early.
• Water Waste: A failing ASO valve can waste hundreds of gallons of water per day. Always check your drain line during the first 24 hours after installing new filters.
• Leak Check: When tapping or adjusting the ASO valve, check all Quick-Connect fittings for "weeping" leaks. Use a dry paper towel to wipe the joints; any dampness indicates the tube is not seated fully into the collet.
• Tank Valve Position: Always ensure the tank valve is fully open. A partially closed valve can restrict flow enough to prevent the ASO from triggering, leading to a constant drain.