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TDS Meter – How to Test Your Water Quality:

The TDS meter is used to test your water’s quality before and after installing the RO system. It can also tell you when the membrane needs to be changed.

Please follow instructions below:

  • Use 2 clean glasses, fill one glass with Tap water, and another glass with Product (filtered) water (rinse this glass with filtered water several times to get an accurate reading).
  • Turn on the meter. The meter will show “000” reading on its screen. Place the TDS meter into the Product water. Record Product water’s TDS reading. Then do the same for the Tap water. Record the Tap water’s reading. Compare the 2 readings.
    • The Product water’s TDS should be about 3%-10% of your Tap water’s TDS. This is a normal range. 

For example:

  • Your Tap water’s TDS: 100 ppm
  • Your Product water’s TDS should read within: 10% of 100ppm => 10ppm 

This means that with 100 ppm input, the RO system has removed 90% of the contaminants (TDS) from the source, leaving only 10% (10 ppm) residual TDS in the Product water. This is a normal range. This means the RO membrane is in good condition. 

If your Product water TDS reads less than 10%, then it is a very good and normal reading.

You should test your water once or twice a year to monitor the membrane condition. As the membrane gets depleted overtime, its rejection capacity will decrease. When this happens, the TDS in the Product water will increase.

When your Product water TDS creeps up to 15%- 20% of input water’s TDS, it’s time to replace the membrane.


If the issue was not addressed, please contact us at:
800-880-4808, or

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