Monitoring Reverse Osmosis System Performance

A properly functioning reverse osmosis system will produce outstanding quality water but how does a system owner know when it's time to replace the reverse osmosis membrane?

As a reverse osmosis membrane ages the percentage of contaminants that it is able to reject decreases.  Stating this another way, the membrane loses it's ability to remove the contaminants dissolved in the raw water.  Over time, there is a slow increase in the quantity of contaminants in the product water.  This process happens so slowly that it is often difficult for the system owner to detect any change in water taste or odor.  The measure of the amount of contaminant in the water is called Total Dissolved Solids - often abbreviated to TDS.  As a membrane ages, the TDS of the product water goes up.  If the TDS gets too high, it's time to replace the membrane.

TDS can be measured very easily using a simple and inexpensive TDS meter.  The user pours a glass of water, immerses the tip of the TDS meter in the water, and records the reading.  By doing this over time, the system user can see if the TDS level in the product water is creeping up.  Changing the reverse osmosis pre-filters on a regular basis will prolong membrane life but eventually the reverse osmosis membrane will need to be changed.  This is done when TDS readings are consistently high.