express water ro5dx making water slow, like a trickle, took forever to fill a glass. help?

Diagnosis

This "trickle" effect in the Express Water RO5DX is typically caused by a failure in the pressure differential between the source water and the storage tank. In a healthy system, the RO membrane slowly fills the pressurized storage tank over several hours; when you open the faucet, the tank's internal air bladder pushes the water out quickly. If you are getting a slow stream, it means you are likely bypassing the tank and receiving "live" water directly from the membrane, which naturally flows at a very slow rate (drops per minute). The root cause is usually one of three things: a depleted pressure bladder in the storage tank, a clogged set of pre-filters (sediment or carbon) restricting the flow to the membrane, or a failed Automatic Shut-Off Valve (ASOV) that prevents the tank from filling. You can confirm this by checking the weight of the storage tank. If the tank feels light but the faucet is trickling, the tank isn't filling. If the tank feels heavy (full of water) but the flow is still a trickle, the tank has lost its air pressure charge.

How to Fix It

Follow these steps in order to restore full flow to your RO5DX system:

1. Check Tank Pressure: Locate the air valve (Schrader valve) on the bottom or side of the storage tank. Use a standard tire pressure gauge to check the PSI. For the RO5DX, the tank should be pre-charged to 7-10 PSI when empty. If it reads 0 PSI, the bladder has leaked or the air has permeated out.
2. Re-pressurize the Tank: Turn off the incoming water supply and open the RO faucet to drain any remaining water. Use a bicycle pump or compressor to add air to the tank valve until the gauge reads exactly 7 PSI. Do not overfill, as this will limit the amount of water the tank can hold.
3. Verify Pre-Filter Integrity: Inspect the three pre-filter canisters. If the sediment filter (Stage 1) looks dark brown or the carbon blocks (Stages 2 and 3) are over six months old, replace them immediately. A clogged pre-filter drops the pressure reaching the RO membrane, which prevents the tank from filling.
4. Test the ASOV: Ensure the Automatic Shut-Off Valve is functioning. If the system continues to send water to the drain line even when the tank is full, the ASOV is stuck open, meaning the tank will never reach the pressure required to push water to the faucet.
5. Flush the System: Once filters are replaced and pressure is set, allow the system to run for 2-3 full tank cycles to clear any air pockets or carbon fines that might be restricting the narrow tubing.

If That Didn't Work

• Replace the RO Membrane: If your pre-filters are new and the tank is pressurized but still won't fill, the RO membrane (Stage 4) is likely fouled or scaled. This happens frequently in areas with high TDS (Total Dissolved Solids). Pull the membrane housing, remove the old element, and install a new high-flow membrane.
• Inspect the Flow Restrictor: The flow restrictor on the waste-water line can become clogged with debris. If the waste line is blocked, the membrane cannot "flush" contaminants away, causing the system to choke and slow the permeate flow to a trickle. Replace the restrictor if you see no water exiting the drain line during the filtration process.
• Check for Kinked Tubing: Because the RO5DX is an under-sink unit, the 1/4" PE tubing often gets pinched by sliding drawers or cleaning supplies. Trace every line from the source to the faucet; even a slight kink can reduce the flow rate by 90%.
• Install a Booster Pump: If your home's incoming water pressure is consistently below 40 PSI, the RO5DX will struggle to push water through the membrane. A permeate booster pump can artificially increase the pressure to 60-80 PSI, significantly increasing the fill rate and faucet flow.

Heads Up

• Pressure Warning: Never pressurize the storage tank while it is full of water; always drain the tank completely before adding air to avoid damaging the internal bladder.
• Filter Schedule: Change the three pre-filters every 6 months and the RO membrane every 24 months to prevent permanent scaling of the membrane housing.
• Sanitization: Whenever you open the system to replace the membrane, wipe the inside of the housings with a diluted bleach solution or food-grade sanitizer to prevent biofilm buildup.
• Leak Check: After tightening any fittings or replacing filters, run the system for 30 minutes and wipe all connections with a dry paper towel to check for "micro-leaks" that can cause cabinet water damage.