User Guide

TDS and water filters
Most water filtration systems have no effect on TDS. That’s because they remove organic
compounds and chlorine disinfectants that cause taste and odor problems but aren’t detected
by TDS meters. While heavy metals are a health concern and contribute to the TDS, their levels
are so low that they hardly impact the TDS level. Water softeners use the ion-exchange process.
The resin beads in the water softener exchange sodium ions for calcium and magnesium ions
(considered as water hardness). Calcium and magnesium minerals are removed but sodium is
released in their place. In this case, the EC has not changed, so TDS meters show little if any
reduction in TDS. The softened water still has a high TDS level; therefore, a TDS is meter is not
suitable for testing water hardness. The best way to monitor water hardness is to use Health
Metric Water Hardness Test Strips.