just got an express water ro5dx, is the water safe to drink if it tastes kinda salty?

Diagnosis

This salty or "brackish" taste in a brand new Express Water RO5DX system is typically caused by one of two things: the presence of factory preservative solutions remaining in the RO membrane or a failure in the membrane's rejection process. When a system is fresh out of the box, the TFC (Thin Film Composite) membrane is often treated with a food-grade preservative to prevent biological growth during shipping. If the system wasn't flushed thoroughly before the first glass of water, these concentrates can leach into the product water, creating a metallic or salty flavor profile. Alternatively, you may be experiencing "salt creep" or a rejection failure. In a functioning RO5DX, the semi-permeable membrane should block 95-98% of dissolved solids. If the membrane is defective or if the wastewater flow restrictor is clogged, the concentrated brine (the salty water) can migrate across the membrane or backflow into the permeate stream. To confirm this, you must use a TDS (Total Dissolved Solids) meter to compare the feed water (tap) against the product water (RO). If the product water TDS is higher than 10% of the feed water TDS, the membrane is not rejecting ions correctly, and the water is not safe for consumption until resolved.

How to Fix It

Follow these precise steps to purge the system and verify the membrane integrity:

1. Complete System Flush: Do not drink the water until you have completely filled and drained the pressurized storage tank at least three times. Open the RO faucet and let it run until the tank is empty. Close the faucet and wait for the tank to refill (this usually takes 2-4 hours depending on your water pressure). Repeat this cycle three times to ensure all factory preservatives are flushed from the membrane and the carbon post-filter.
2. Check the Auto-Shutoff Valve (ASV): Ensure the ASV is functioning. If the system doesn't shut off when the tank is full, it can cause pressure imbalances that push brine into the clean water line.
3. Verify Drain Line Installation: Check the black 1/4" drain line. Ensure the flow restrictor (the small plastic cylinder) is installed in the correct direction and that the line is not kinked. If the brine cannot exit the system, the salt concentration builds up and "leaks" through the membrane via osmotic pressure.
4. TDS Testing: Use a digital TDS meter. Measure the tap water (e.g., 300 ppm). Then measure the RO water. If the RO water is below 30 ppm, the salty taste is likely just residual preservative and will disappear after another flush. If the RO water is above 50 ppm, the membrane is faulty.

If That Didn't Work

• Replace the RO Membrane: If the TDS reading remains high after three tank flushes, the membrane may have been damaged during shipping or is a "lemon." Replace the membrane element (typically the large center cartridge) with a high-rejection 50 GPD membrane. Ensure the O-rings are lubricated with food-grade silicone grease to prevent leaks.
• Inspect the Check Valve: There is a small check valve located at the outlet of the membrane housing. If this valve is leaking or stuck open, product water can flow backward, mixing with the brine stream and introducing a salty taste. Replace the check valve if you hear a constant "hissing" or "clicking" sound from the housing.
• Check Feed Water Pressure: The RO5DX requires a minimum of 40 PSI to function correctly. If your home water pressure is too low (below 35 PSI), the membrane cannot effectively push water through the pores, and the rejection rate drops significantly, allowing salts to pass through. You may need to install a permeate pump or a booster pump.
• Verify Post-Carbon Filter Seating: Ensure the final polishing filter (the horizontal one before the faucet) is snapped in tight. If there is a leak at the connection, it can introduce air or contaminants that alter the taste, though this rarely causes a "salty" flavor specifically.

Heads Up

• Avoid "First Glass" Syndrome: Always discard the first 2-3 glasses of water after the system has been sitting idle for several hours; the water sitting in the lines can accumulate a higher TDS concentration.
• Pressure Tank Maintenance: Every 6 months, check the air pressure in the storage tank using a tire gauge. It should be between 7-10 PSI when the tank is empty. Low pressure can lead to sluggish flow and taste inconsistencies.
• Filter Schedule: Change the three pre-filters (sediment and carbon) every 6 months. If these clog, the membrane is exposed to chlorine, which will permanently "burn" the membrane and cause it to stop rejecting salt.