RO Perm - TDS Test

How to Use the TDS Meter

The TDS* meter is used to test your water's quality before and after the RO system. It also tells you when the membrane needs to be changed.

Please follow instructions below:

Use 2 clean glasses, put the Tap water in one glass, and the Product (filtered) water in the second glass (rinse this glass with filtered water several times to get an accurate reading).

Place the TDS meter into the Tap water. Turn on the meter by holding down on the black button on top of the meter. The meter will give a digital "ppm" reading on its screen. Record the Tap water's reading. Then do the same for the Product water. Record the Product 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:

If your Tap water's TDS is 100 ppm --> then your Product water's TDS should read between 3% (3ppm) to 10% (10ppm) of your input water's 100ppm.

This means that with 100 ppm input, the RO system has removed 90% - 97% of the contaminants (TDS) from the source, leaving only 3%-10% (3 ppm -10 ppm) residual TDS in the Product water. This means the RO membrane is in good condition.

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

When the Product water's TDS reaches 15%-20% of input water's TDS, then it's time to change the membrane.

*TDS = Total Dissolved Solids consist mainly of carbonates, bicarbonates, chlorides, sulfates, phosphates, nitrates, calcium, magnesium, sodium, potassium, iron, manganese, and a few others. They do not include gases, colloids, or sediment. The TDS can be estimated by measuring the specific conductance of the water. Dissolved solids in natural waters range from less than 10 mg/l for the rain to more than 100,000 mg/l for brines. Since TDS is the sum of all materials dissolved in the water, it has many different mineral sources.

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