For a 125,000-gallon pool with a Combined Chlorine reading of 0.4 ppm, how much chlorine is needed for complete removal?

To determine how much chlorine is needed for the complete removal of combined chlorine, it's essential to recognize that the general guideline for breaking down combined chlorine usually involves adding a dose of chlorine that is approximately equal to the existing combined chlorine level, plus a little extra to ensure effective removal.

In this scenario, the pool has a Combined Chlorine reading of 0.4 ppm. The common practice recommends adding 1 ppm of chlorine over the current combined chlorine level to achieve effective oxidation of the chloramines and other forms of combined chlorine.

So if you start with the 0.4 ppm of combined chlorine and require an additional approximately 3.6 ppm to reach optimal residual levels for effective sanitation, rounding this number would lead you to aim for a chlorine level of around 4.0 ppm. This practice ensures that the combined chlorine is adequately addressed, and it contributes to maintaining overall water quality by ensuring a sufficient free chlorine concentration.

Thus, adding 4.0 ppm of chlorine is not only sufficient for breaking down the combined chlorine present but is also aligned with established treatment methods for ensuring clean and safe swimming pool water.