The water level for both your pool and spa should be at the middle of the tile under the coping.
Letting your water get too low can cause your skimmers to dry out and stop pumping water to the pool pump. In turn, the pool pump will go out.
During the hottest days, up to 1/4″ loss of water per day can be expected, so be sure to add water as necessary.
A UV sanitizer can dramatically reduce or eliminate the use of chlorine when used in combination with other sanitizers.
It is recommended to run the filter pump during the heat of the day (or overnight during seasons of overnight freeze) long enough to achieve at least one turnover of water thorough the filter per day.
Install a freeze protection device or manually switch all pumps on during freezing weather.