Due to the high temperatures of hot tub water, and its resulting evaporation, the total number of dissolved solids in the water will increase over time despite regular chemical maintenance. For this reason, you must periodically drain and re-fill your hot tub water. Failure to change your water within a timely manner can cause your hot tub's filters to get dirty sooner, put extra pressure on the pump, and reduce the efficiency of your hot tub’s heater. It can be difficult to know exactly when your hot tub water needs to be changed, but as a general rule of thumb, we say that water should be...