Total Dissolved Solids (TDS) is a measurement of the total amount of matter (minerals, chemical residue, and other particles) that remains in water. The primary contributing factor that leads to TDS is evaporation. As water evaporates, only the water itself evaporates. Minerals, chemical residue, and other particles are left behind and remain in the pool water. With evaporation, you need to continually add water. As you add tap water up to the standard operating water level (half way up the skimmer), you are also adding additional minerals and particles. Although these minerals and other particles from tap water do add to the TDS reading, it is extremely minimal. The biggest factor is that this new tap water will soon be introduced to chemicals. It is the chemical residue that is not filtered and remains in the pool water that has the greatest effect on increasing TDS. Whenever chemicals are added, the TDS reading will increase.

The process of evaporation is continuous. As water evaporates, matter within it is left behind and will remain in the water. Eventually, this matter that remains in the pool water will act as a sponge, consuming your new chemicals, rendering them virtually ineffective. It will take many years (approximately 6-8 years) for the TDS reading to become so high that it will consume your chemicals before they can engage in their intended purpose; 6-8 years is a guideline only. Click HERE for a TDS chart.

There is no chemical that can lower the TDS reading into an ideal range. Rather, a TDS reading can only be lowered by draining your pool, either partially or completely, and adding fresh water. If it has been some time since your pool was last drained and cleaned, there are certain indicators that may tell you that your TDS reading has probably reached or surpassed its maximum parameters:

• Continual addition of excess chemicals.
• Water chemistry tests fine, but water is still not clean, clear, blue and sparkling. Various water chemistry problems include:
  • Colored yet clear water (the water has an odd tint, but you can still see the pool floor).
  • Algae growth despite a good chlorine (or its alternative) reading and proper overall water chemistry (pH and Alkalinity).
• Varying and false readings on chemical tests.

If any of these are the case with your pool, or if other water chemistry issues arise, despite the continual testing and addition of chemicals, the TDS reading has either met or exceeded the maximum. Again, you can only lower TDS by draining the pool, either partially or completely. Poolmanual.com recommends that you contract your local pool professionals and pay them to perform a drain and clean, it really is more of an investment than a service call.