Cara's Pool School — drain pool

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...

A temporary drain and refill is acceptable during the winter. However, leaving a pool drained for any prolonged period of time could lead to drying out, cracking (plaster), or even structural shifting because of the void left from the absence of the water's weight on the shell.

It's recommended to drain when TDS (total Dissolved Solids) levels reach or exceed about 2000 - 2500 ppm, or roughly 1500 ppm more than fresh-fill. Other reasons, such as high CYA levels or other concerns, may require draining on an as-needed basis.