Simply enter your Feed Water TDS and RO Water TDS into the boxes above and click "Submit". The percentage of TDS (total disolved solids) rejection will be displayed. We normally recommend membrane replacement once you drop below 75%. This may vary in areas with high TDS in the feed water. Let the tap water and reverse osmosis water run for a few seconds before drawing your sample.
See our selection of TDS meters under Water Tests. Knowing the rejection rate is the only wat to know if it is time to replace your reverse osmosis membrane.