TDS Helper

Understanding Total Dissolved Solids in Swimming Pools

Total Dissolved Solids, or TDS, is the combined amount of dissolved material in pool water. It includes salt, calcium, alkalinity, stabilizer, metals, and the leftover byproducts of chemicals added over time.

What Raises TDS?

• Salt added for a saltwater chlorine generator.
• Calcium, alkalinity, and stabilizer products.
• Repeated chemical additions.
• Metals and minerals in fill water.
• Evaporation, which leaves dissolved material behind.

When TDS Matters

TDS by itself does not always indicate a problem. Saltwater pools naturally have much higher TDS than traditional chlorine pools because of the salt level. The number is more useful when compared with the source water and the pool’s normal operating history.

Possible Signs of Excessively High TDS

• Persistent cloudy water that is not explained by filtration or chemistry.
• Difficulty maintaining stable water balance.
• Unusual taste or feel.
• Repeated scaling or corrosion concerns.
• A large increase above the original fill-water TDS.

How TDS Is Reduced

There is no chemical that truly removes all dissolved solids from pool water. The practical way to lower TDS is partial water replacement. Before draining, confirm the reading, review local discharge rules, and consider the pool type and groundwater conditions.