The levels of chemical pollution present in the pool water can be measured using an instrument called a ‘Total Dissolved Solids’ meter (TDS meter). This measures the electrical conductivity of the pool water. As pure water is not a conductor of electricity, the more conductive the swimming pool water is, the more it must contain by way of elements other than water, i.e. it is the chemicals dissolved within the swimming pool water that is conducting the electricity, not the water itself.
The levels of chemical pollution need to be kept under control, otherwise the pool will look cloudy and unclean and will also cause a bad ‘chlorine smell’ and cause bathers discomfort through eye irritation and rashes etc.
The TDS level of the swimming pool should be kept well below 1000mg/m3 above the TDS level of the mains water supply.
The best way of controlling chemical pollution is via prevention. Minimising the amount of chemical pollution being introduced into the pool via bathers is the first step. This will then lead to the pool operator not having to add as much disinfectant to the pool, which leads to not having to add as much pH correctant onto the pool either. Bather pre-showering is the most effective way of minimising the amount of chemical pollution that bathers introduce into the swimming pool water.
Chemical pollution can also be controlled re-actively (after the pollution has entered the water) by a process of dilution, which is where an adequate supply of clean, fresh water (usually from the mains supply) is introduced into the pool on a regular basis. The recommended rate of dilution is 30 litres of fresh water to be added per bather, per day.