Instructions – Understanding your TDS Meter

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Reverse osmosis (RO) systems remove dissolved solids from water. The more dissolved solids water contains the better it conducts electricity. A TDS (total dissolved solids) monitor measures how well the water conducts electricity and therefore can determine the total concentration of dissolved solids in the water. This measurement is expressed as milligram per liter (mg/L).

Air & Water Quality installs an in-line dual TDS monitor with point of use reverse osmosis systems to monitor the TDS of the raw untreated water and the purified water. With time, the ability to reduce TDS will decrease and the membrane will need to be replaced.

Monitor Operation:
1. If the display is blank, press the “on/off” button.
2. Run some water from the RO faucet.
3. Slide the white switch under the display to the left(IN) to read the TDS of the untreated (raw water) in the display.
4. Slide the white switch under the display to the right (OUT) to read the TDS of the treated (RO water) in the display.
5. To determine the greatest value you should see for a newly installed system’s OUT value, multiply the IN value by 0.05. The membrane should be changed when the OUT value exceeds the IN value multiplied by 0.15. The target level is always 85% reduction or better.

Example: The IN (raw water) value is 200. A RO system with a properly working membrane should have an OUT(treated water) value that does not exceed-
200 X 0.15 = 30

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