User Guide

water contains salts, algae, and other microbes that must be rinsed from the probe after each
use. The TDS of saltwater is around 10,000 ppm and cannot be measured by Health Metric TDS
meters.
TDS in pools and spas
The ideal TDS level in pools and
spas is an area of debate. Most
experts agree that the maximum
TDS of a freshwater pool or spa
should be no higher than 1,500
ppm. But, as water evaporates and
as pool chemicals are added, the
TDS can climb closer to 3,000 ppm.
Saltwater pools that use a salt
generator normally have a TDS
level of 3,500 ppm up to 5,000 ppm. The TDS measurement is helpful for detecting a trend of
increasing TDS, which indicates a build-up of minerals or pollutants in the water. Simply place
the TDS meter in the water and take the measurement. Rinse the meter with freshwater after
use.
Note: A TDS meter is not suitable for testing water hardness. The best way to monitor water
hardness is to use Health Metric Water Hardness Test Strips.
Measuring pool salt levels
TDS meters can be used for estimating salt levels by using a conversion factor. Multiply the TDS
level by 0.9 to obtain a ppm salt level. This is a rough approximation of the actual NaCl level.
Pool salt meters are actually TDS meters that automatically perform this calculation. Note that
some manufacturers use a different conversion factor to calculate the salt level. You may find
that another meter or pool store will provide a different salt level due to this factor.