Why is a drain and refill necessary, and how often should it be done?

Unfortunately, timing and the need to drain can vary from pool to pool since it depends heavily on usage and chemistry.

Aside from repair needs and other exceptional circumstances, pools should be drained whenever the Total Dissolved Solids (TDS) levels exceed roughly 2000 - 2500 ppm.

At these levels, water will have a difficult time in accepting chemicals intended to properly balance parameters and could be inclined to promote staining and discoloration. It is recommended to have a full water test performed monthly by your local and trusted pool professional, in order to effectively monitor TDS levels and other potential concerns.