my system seems to be draining water constantly, like i can hear it running to the drain pipe non-stop, even when the tank is full.

Diagnosis

The constant flow of water to the drain line in the iSpring RCC7AK system indicates a failure in the Automatic Shut-Off (ASO) valve. 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 internal diaphragm pushes a piston to block the feed water. When this happens, the entire system goes silent. If you hear a constant "hissing" or trickling sound at the drain saddle, the valve is failing to trigger this shut-off. This typically happens due to two reasons: either the internal rubber diaphragm has perished or a small piece of sediment/scale has lodged in the valve seat, preventing the piston from closing fully. You can confirm this is the root cause by closing the blue tank valve. If the water continues to run to the drain even with the tank closed and the faucet off, the ASO valve is mechanically stuck or leaking internally. If the water stops when the tank is closed but starts again and never stops when the tank is open, the valve is likely failing to sense the pressure increase from the tank.

How to Fix It

To resolve this, you must first attempt to unstick the valve and then replace it if the mechanical failure persists. Follow these exact steps:

1. Shut off the cold water supply valve connected to the system and close the blue storage tank valve to isolate the system.
2. Locate the ASO valve. It is the small, black rectangular plastic component with four quarter-turn tubing ports.
3. While the water supply is on, gently tap the sides of the ASO valve housing using the plastic handle of a screwdriver. Sometimes this vibration is enough to dislodge a grain of sediment and allow the internal piston to snap shut.
4. If tapping fails, you must replace the valve. Disconnect the four 1/4" polyethylene tubes from the ASO valve by pushing down on the collets (the small rings) and pulling the tubing out.
5. Slide a new ASO valve (Part # RCC7AK-ASO) into place. Ensure the tubes are pushed firmly into the ports until they bottom out; if they are not fully seated, you will have a leak that prevents the system from ever reaching the pressure needed to trigger the shut-off.
6. Slowly open the feed water valve and check for leaks. Open the tank valve and allow the system to fill. Once the tank is full, listen for the silence that indicates the valve has successfully closed the loop.

If That Didn't Work

• Check the Check Valve: If the ASO valve is new but water still drains, the one-way check valve (located at the permeate port of the membrane housing) may be leaking. If this valve fails, water flows backward from the tank into the membrane and out the drain, creating a continuous loop. Replace the check valve elbow to stop this "back-pressure" leak.
• Inspect the Membrane Integrity: If the RO membrane has developed a tear or "channeling," the pressure differential required to trigger the ASO valve may never be reached. If the system runs for 24+ hours without stopping despite a new ASO valve, replace the RO membrane element.
• Verify Tank Pressure: A ruptured bladder in the storage tank can prevent the system from reaching the shut-off pressure. Use a tire gauge to check the air valve at the bottom of the tank; it should be between 7-10 PSI when the tank is empty. If it is 0 PSI or leaking air, the tank must be replaced.
• Check for Kinked Tubing: Ensure the line leading from the ASO valve to the membrane housing is not pinched. A restriction here can cause erratic pressure readings, preventing the valve from sealing.

Heads Up

• Always use a small piece of 1/4" tubing cutter for clean, square cuts. If you use scissors, the tube will be crushed, leading to slow leaks at the ASO valve ports.
• Avoid over-tightening the tubing collets; they are "push-to-connect" and rely on an internal O-ring. Forcing them too hard can crack the plastic housing.
• Perform a "flush" of the system after replacing any valve by opening the RO faucet for 5 minutes to clear any trapped air bubbles that can cause "hammering" noises.
• Check your home's incoming water pressure. If your house pressure is below 40 PSI, the ASO valve may struggle to trigger, and you may require a permeate pump or a booster pump to ensure the system shuts off correctly.