my apec ro system tank seems to have low pressure, water just dribbles out of the faucet

Diagnosis

The APEC ROES-50 utilizes a pressurized diaphragm tank to store purified water. Inside the tank, a rubber bladder separates the stored water from a pocket of compressed air. This air acts as a spring; as the RO membrane slowly fills the tank, the air compresses, creating the pressure necessary to push water up through the faucet when you open the valve. When you experience a "dribble" despite the tank feeling heavy with water, it indicates a loss of this air pre-charge. This pressure loss typically occurs due to microscopic leaks around the Schrader valve or gradual permeation through the bladder material over several years. To confirm this is the issue, lift the tank. If the tank feels heavy (indicating it is full of water) but only a small amount of water flows out before the pressure drops to nothing, the air bladder has lost its charge. If the tank is light and empty, the issue is likely a fouled membrane or a closed feed valve rather than a tank pressure problem.

How to Fix It

To restore the pressure in your APEC ROES-50 storage tank, you will need a standard bicycle pump or a small automotive compressor with a pressure gauge.

1. Close the cold water feed valve located at the wall or under the sink to stop new water from entering the system.
2. Open the RO faucet and let all the water drain out completely. This is critical; if you add air while the tank is full of water, you will create a "hydraulic lock" and cannot get an accurate pressure reading.
3. Locate the air valve (Schrader valve) on the side or bottom of the blue tank. Remove the plastic protective cap.
4. Attach your pressure gauge to the valve. A completely depleted tank will read 0 PSI.
5. Slowly add air into the tank. Use short bursts to avoid overheating the valve.
6. Pump the tank until the gauge reads exactly 7 to 8 PSI. Do not exceed 10 PSI, as over-pressurizing can rupture the internal bladder or prevent the RO membrane from filling the tank.
7. Remove the gauge and replace the plastic cap securely.
8. Close the RO faucet and reopen the cold water feed valve.
9. Allow the system to fill completely (this may take 2-4 hours depending on your water temperature and TDS levels) before testing the flow at the faucet.

If That Didn't Work

• Check for a Ruptured Bladder: Depress the small pin inside the Schrader valve briefly. If water squirts out of the air valve instead of air, the internal rubber bladder has ruptured. This is a non-repairable failure. You must replace the entire storage tank (Part number: APEC-TANK).
• Inspect the Auto Shut-Off Valve (ASO): If the tank remains empty even after recharging, the ASO valve may be stuck. This valve shuts off the water supply once the tank reaches pressure. If it fails in the "closed" position, the tank will never refill. Tap the ASO valve gently with a screwdriver handle to see if flow resumes.
• Test the RO Membrane: If the tank is empty and the ASO is working, your membrane may be fouled. Place a graduated cylinder under the waste water line. If the waste line is flowing but the tank isn't filling, the membrane is likely exhausted and needs replacement (Model: Dow Filmtec or APEC equivalent).
• Verify Feed Water Pressure: Ensure your home's incoming water pressure is at least 40 PSI. If your home pressure is too low, the ROES-50 cannot overcome the osmotic pressure required to push water into the storage tank.

Heads Up

• Pressure Maintenance: Check your tank air pressure once every 12 months. It is common for these tanks to lose 1-2 PSI per year.
• Avoid Over-inflation: Never use a high-pressure air compressor without a regulator. Pumping a tank to 30 or 40 PSI will permanently damage the bladder and significantly reduce your usable water capacity.
• Sanitization: Whenever you open the system or replace the tank, it is highly recommended to sanitize the lines using a diluted bleach solution or a specialized RO sanitizing kit to prevent biofilm buildup.
• Temperature Effects: In winter months, your RO system will produce water significantly slower. If you notice a slight dip in pressure during January or February, it may be due to water temperature rather than a leak.