User Guide

Reverse osmosis (RO) filtration does reduce TDS because it physically removes salts, minerals,
and other current-conducting ions from the water. The TDS of RO water should be much lower
than the untreated water feeding the RO system. A properly functioning RO system will remove
from 70% to 99.9% of the TDS. When an RO system starts removing less than 70% of the
incoming TDS, it is time to replace the reverse osmosis membrane and have the system
serviced.
Example Calculation
 Incoming water: 300 ppm TDS
 RO water: 30 ppm TDS
 90% of the TDS is being removed = OK
If RO water = 120 ppm TDS, only 60% of the TDS is being removed. The system needs service.
How to test the TDS of tap water
Turn on the cold water and let it run
for about one minute. Take a water
sample in a clean plastic or glass
container. Place the TDS meter up
to the immersion level in the
sample and wait for the reading to
stabilize. By gently swirling, the
meter will help prevent water
bubbles from collecting near the
two metal probes. TDS meters
automatically lock and hold the stabilized TDS level. Rinse in clean water and shake off excess
water. Refer to the user manual for more detailed instructions.
How to test bottled water
“Bottled water” is a generic term with no definition other than it is water that is fit for human
consumption. Spring water, distilled water, filtered water, and purified water are all different