Why Is My RO System's Drain Line Always Running?
The Causes of Constant Draining and How to Stop Water Waste
A reverse osmosis system is designed to produce pure water and send the rejected, contaminated water to the drain. However, a constant stream of water to the drain when the tank is full is a sign of a problem. This not only wastes water but can also lead to higher utility bills. Understanding the cause is the first step to a solution.
The most likely culprit is a faulty Automatic Shut-Off Valve (ASOV). The ASOV is a key component that stops the flow of water to the membrane and the drain once the storage tank has reached approximately 60-65% of the incoming water pressure. If the valve is not functioning correctly, it will fail to close, and water will continue to flow to the drain. You can test the ASOV by disconnecting the line from the storage tank. If the water still flows to the drain, the ASOV is the problem and needs to be replaced.
Another common cause is a clogged or improperly sized flow restrictor. The flow restrictor is a small plastic component in the drain line that regulates the amount of water flowing to the drain. It is designed to create back pressure on the membrane to ensure efficient operation. If it becomes clogged with sediment or scale, it can cause the drain line to run continuously or become completely blocked. Check the flow restrictor and clean it or replace it if it's clogged. Make sure you are using the correct size flow restrictor for your system's membrane capacity.
Finally, a ruptured or damaged RO membrane can also cause constant draining. While less common, a membrane with a hole or tear will not create the necessary back pressure, and water will simply flow through to the drain without being properly filtered. If you have ruled out the ASOV and flow restrictor, a new RO membrane might be the answer.
The most likely culprit is a faulty Automatic Shut-Off Valve (ASOV). The ASOV is a key component that stops the flow of water to the membrane and the drain once the storage tank has reached approximately 60-65% of the incoming water pressure. If the valve is not functioning correctly, it will fail to close, and water will continue to flow to the drain. You can test the ASOV by disconnecting the line from the storage tank. If the water still flows to the drain, the ASOV is the problem and needs to be replaced.
Another common cause is a clogged or improperly sized flow restrictor. The flow restrictor is a small plastic component in the drain line that regulates the amount of water flowing to the drain. It is designed to create back pressure on the membrane to ensure efficient operation. If it becomes clogged with sediment or scale, it can cause the drain line to run continuously or become completely blocked. Check the flow restrictor and clean it or replace it if it's clogged. Make sure you are using the correct size flow restrictor for your system's membrane capacity.
Finally, a ruptured or damaged RO membrane can also cause constant draining. While less common, a membrane with a hole or tear will not create the necessary back pressure, and water will simply flow through to the drain without being properly filtered. If you have ruled out the ASOV and flow restrictor, a new RO membrane might be the answer.