A reverse osmosis (RO) system is designed to drain water only during the purification cycle. If your iSpring RO system is constantly draining, even when the tank is full and the faucet is off, this indicates a malfunction in one of the system’s key components.
The most common causes of a continuously draining iSpring RO system are a failed ASO valve, incorrect tubing setup, or tank pressure issues.
This guide explains how to diagnose and fix the issue.
Common Causes and How to Fix Them
1. Faulty or Incorrectly Installed Auto Shut-Off (ASO) Valve
The ASO valve is responsible for stopping the flow of water to the drain once the tank is full. If installed backward or damaged, the valve will not close properly and the system will continue draining water.
How to fix:
- Check that the ASO valve is correctly oriented and that all tubing is routed according to your system manual diagram.
- Make sure the line from the membrane to the ASO is connected to the correct port, and the tank line is going to the designated ASO port.
- If you suspect damage, replace the valve.
2. Failed Check Valve
The check valve prevents water from flowing backward from the tank into the membrane. If this valve fails, pressure will not build in the tank and the ASO valve will never trigger to shut off the system.
The check valve is usually integrated into the elbow fitting on the outlet side of the membrane housing. It’s not labeled in most iSpring manuals but is essential for shutting off the system when the tank is full.
How to fix:
- Inspect the check valve. Note, the check valve is usually integrated into the elbow fitting on the outlet side of the membrane housing. It’s not labeled in most iSpring manuals but is essential for shutting off the system when the tank is full.
- To test, disconnect the line to the tank and see if water flows backward. If it does, the check valve needs to be replaced.
3. Incorrect, Missing, or Clogged Flow Restrictor
The flow restrictor is a small but essential component that controls the amount of water sent to the drain. It creates back pressure, allowing the system to shut off properly when the storage tank is full.
If the restrictor is missing, the system will constantly drain. If it’s clogged, water may stop flowing to the drain entirely, which can disrupt system function and potentially damage components.
How to fix:
- Confirm that the correct flow restrictor is installed on the black drain tubing coming from the membrane housing.
- If you suspect a clog, disconnect the black tubing from the drain saddle while the RO faucet is open and the system is running. You should see a narrow, steady stream of drain water. If no water flows, the restrictor is likely clogged and should be replaced.
- Clean or replace the flow restrictor as needed. Reconnect tubing and verify proper drain function after reassembly.
4. Low or Leaking Tank Pressure
If the tank cannot hold sufficient pressure, the system will continue trying to fill it, causing ongoing drainage. The ASO valve relies on back pressure from the tank to know when to shut off.
How to fix:
- Disconnect the tank and use a tire pressure gauge to check the air pressure. When empty, it should read between 7 and 10 psi.
- If it is lower, use a hand pump to increase pressure.
- Check for leaks or a ruptured bladder if the tank doesn’t hold pressure.
5. Misconnected Tubing
Incorrect tubing connections can prevent the system from shutting off properly. iSpring systems use color-coded tubing for clarity.
How to fix:
- Confirm that the red tubing connects to feed water, black to drain, yellow to the tank, and blue to the faucet.
- Compare your setup to the model diagram provided in your manual.
Diagnostic Test: Is It the Tank or the Valve?
To test whether the issue is related to the tank or the control valves:
- Close the shut-off valve on the tank.
- Leave the system running for a few minutes.
- If water continues to drain, the issue lies with the ASO valve, flow restrictor, or check valve.
- If water stops draining, the problem is most likely with the tank or its valve.
Preventative Tips
- Replace your filters and membrane as recommended to maintain system pressure and performance.
- Avoid installing the system on hot water lines, which can damage internal components.
- After changing filters, flush the system according to manual instructions to prevent airlock or backpressure issues.