the tds reading on my screen is still high, like over 50, even with new ro membranes. tastes fine though.

Diagnosis

The elevated TDS reading on your Waterdrop G3P800, despite a perceived "clean" taste and new membranes, is typically caused by one of two things: sensor fouling or "TDS creep." Because the G3P800 uses a digital conductivity probe to estimate dissolved solids, any mineral buildup (scale) on the probe's electrodes will create a false resistance reading, tricking the onboard computer into reporting a higher PPM (parts per million) than what is actually present in the water. Furthermore, if the system has been sitting idle for several hours, you are likely experiencing TDS creep. This happens when small amounts of concentrated solutes migrate across the RO membrane via osmosis while the water is stagnant. This doesn't mean the membrane is failing; it means the first few glasses of water in the reservoir hold a higher concentration of minerals. To confirm if this is a sensor error or a membrane issue, you should use a handheld independent TDS meter to test the water at the faucet. If the handheld meter reads 10-20 PPM but the G3P800 screen reads 50+ PPM, the internal sensor is out of calibration or dirty.

How to Fix It

To resolve the high reading and stabilize the new membranes, follow this precise sequence to flush the system and clear the sensor:

1. Perform a high-volume flush. Activate the faucet and let the water run continuously for 15 to 20 minutes. This isn't just about the water in the tank, but about forcing a high flow rate through the new RO membranes to strip away the preservative solution used during factory packaging.
2. Power cycle the system. Unplug the G3P800 from the wall outlet for exactly 60 seconds. This resets the logic board and forces the TDS sensor to re-initialize its baseline reading upon reboot.
3. Check for air pockets. If you recently changed the membranes, air bubbles can get trapped around the sensor probe, causing erratic readings. Tilt the unit slightly (about 10 degrees) while the water is running to help air escape the internal housing.
4. Verify the "Pure" water line connection. Ensure the tubing leading from the membrane housing to the sensor assembly is seated firmly with the quick-connect fittings pushed all the way in. A slight leak here can introduce raw source water into the sensor chamber.

If That Didn't Work

• Manual Sensor Cleaning: If the reading remains high, the probe may have calcium scaling. While the sensor is integrated, you can often clear it by running a small amount of food-grade citric acid or a mild white vinegar solution through the system. Fill a separate container with a 10% vinegar solution, feed it into the system manually if possible, or let it sit in the tank for an hour before flushing.
• Check the Auto-Shutoff Valve: Inspect the 4-way shutoff valve. If the valve is leaking internally, "raw" water can bypass the membrane and mix with the purified water right before it hits the sensor, causing a spike in TDS. Look for any moisture around the valve housing.
• Verify Source Water TDS: Use a handheld meter to check your incoming tap water. If your source water is exceptionally high (over 500 PPM), the G3P800's membrane may require a longer "break-in" period of 48 hours of active use before the TDS reading stabilizes to its lowest point.
• Replace the Pre-Filter: If the sediment and carbon pre-filters are clogged, the pressure reaching the RO membrane is reduced. Low pressure leads to higher solute passage, which increases the TDS reading. Replace the pre-filter set even if they aren't "due" yet to ensure maximum PSI at the membrane surface.

Heads Up

• TDS Creep is Normal: Do not panic if the first glass of the day reads 40 PPM and the fifth glass reads 10 PPM. This is a physical property of RO systems and not a defect in the G3P800.
• Avoid Over-Flushing: While a 20-minute flush is good for new membranes, doing this daily will prematurely wear out your pre-filters and waste significant amounts of water.
• Calibration Limits: The G3P800 sensor is factory-calibrated. If the discrepancy between a handheld meter and the screen is more than 30 PPM after a full flush, the sensor module itself may be defective and require a warranty replacement.
• Water Temperature: Extremely cold incoming water can increase the TDS reading on the screen because the viscosity of the water changes, affecting the conductivity probe's accuracy.