One of the most common questions we receive is, “How do I know if my reverse osmosis drinking water system is working properly?”

The easiest way to test a reverse osmosis system is by using a TDS meter. TDS stands for Total Dissolved Solids, and these meters are inexpensive, easy to use, and widely available online. Most TDS meters cost between $5 and $20, although more advanced models are available.

A TDS meter allows you to measure the amount of dissolved solids in your water before and after it passes through the reverse osmosis system. This gives you a simple way to verify that your system is removing contaminants and producing high-quality drinking water.

To perform the test, collect a sample of your untreated water and place the TDS meter into the sample. For this demonstration, the incoming water measured 121 parts per million (PPM) of total dissolved solids.

Next, test the water produced by the reverse osmosis system. A properly functioning reverse osmosis membrane should typically achieve a rejection rate of 90% to 95% or higher. In many cases, a brand-new membrane can achieve even better performance.

For example, if your incoming water measures 121 TDS, you would generally expect the reverse osmosis water to test at approximately 12 TDS or lower. If the system is consistently producing higher readings and the rejection rate falls below 90%, it may indicate that the membrane is beginning to foul and should be evaluated for replacement.

The reverse osmosis membrane is the primary filtration component in the system and is typically the most expensive filter to replace. Monitoring TDS levels periodically can help you determine when maintenance may be needed and provide peace of mind that your drinking water system is performing as expected.

As a general rule, most residential reverse osmosis systems should maintain a rejection rate between 90% and 95% throughout the life of the membrane. If your incoming water has a TDS level of 400, for example, you should still expect the treated water to be significantly lower when the system is functioning correctly.

Using a TDS meter is one of the simplest and most effective ways to verify the performance of your reverse osmosis drinking water system. Regular testing helps ensure your system continues to provide high-quality purified drinking water for your home.