just installed my apec roes-50 and the tank won't fill up at all, zero water coming out

Diagnosis

When a newly installed APEC ROES-50 fails to fill the storage tank, the primary culprit is almost always an "air lock" within the membrane housing or a failure to properly initiate the flow through the check valve. Because the ROES-50 uses a high-pressure membrane, air bubbles can become trapped in the upper dome of the housing, creating a pocket of resistance that prevents water from reaching the permeate tube (the small line leading to the tank). If the air pressure is high enough, it effectively blocks the water from entering the membrane, meaning the system will simply send all water down the drain line without any filling the tank. Another common cause is a stuck or improperly seated one-way check valve. This valve is located at the exit of the membrane housing; its job is to prevent water already in the tank from flowing backward through the membrane. If this valve is stuck closed or if the tubing is kinked at the connection point, the water cannot move forward into the storage tank. You can confirm this by checking the drain line: if water is constantly flowing to the drain but the tank remains empty after 4-6 hours, you have a flow blockage or an air lock rather than a leak.

How to Fix It

To resolve an air lock and prime the ROES-50 system, follow these precise steps:

1. Close the cold water feed valve and the blue storage tank valve (turn clockwise until tight).
2. Open the RO faucet on your sink and leave it open; this relieves the internal pressure.
3. Locate the tubing that enters the membrane housing (the largest horizontal canister). Carefully disconnect the tubing from the "Inlet" port of the membrane housing.
4. Place the end of this tubing into a plastic bucket.
5. Slowly open the cold water feed valve. You will see water flow into the bucket. This process pushes the trapped air out of the pre-filters and ensures the membrane inlet is fully primed with water.
6. Once the water flow is steady and bubble-free, reconnect the tubing to the membrane housing inlet, ensuring the push-fit connector is seated fully (push it in until you feel a second "click").
7. Close the RO faucet and open the blue storage tank valve.
8. Wait 3 to 5 hours. The tank will not fill instantly; it typically takes several full cycles to reach the 2.0 to 3.0 gallon capacity.

If That Didn't Work

• Check the Automatic Shut-Off Valve (ASO): The four-way valve (where four tubes meet) may be malfunctioning. If the internal diaphragm is stuck, it may be signaling the system to stop producing water even when the tank is empty. Gently tap the side of the ASO valve with a plastic screwdriver handle to see if it releases.
• Inspect the Check Valve: Remove the small plastic check valve located at the membrane housing outlet. Try blowing air through it; if you cannot blow air in the direction of the tank, the valve is defective and must be replaced.
• Verify Feed Water Pressure: Use a pressure gauge on your main line. The ROES-50 requires a minimum of 40 PSI to function. If your home pressure is below 40 PSI, the water will not have enough force to overcome the osmotic pressure of the membrane, and the tank will never fill.
• Check for Kinked Tubing: Examine the 1/4" poly tubing, specifically where it enters the tank and the membrane housing. Even a slight pinch in the line can restrict flow enough to prevent the tank from pressurizing.

Heads Up

• Initial Flush: Always discard the first two full tanks of water. The ROES-50 membrane contains a food-grade preservative that must be flushed out before drinking.
• Leak Check: After priming the system, apply a small amount of soapy water to every push-fit connection. If you see growing bubbles, the tubing isn't cut square or isn't pushed in far enough.
• Tank Pressure: If the tank feels heavy but no water comes out of the faucet, the air bladder in the tank may have lost pressure. Use a tire gauge to check the valve (usually located at the bottom of the tank); it should be between 5 and 7 PSI when empty.
• Filter Replacement: Change the first three pre-filters every 6 months to prevent sediment from clogging the membrane, which would lead to the same "no fill" symptom.