I drain my pool half way every winter. So half fresh each year plus, weekly backflows after cleaning which flush the filters and topoff with fresh water.

It is a big ass pool and runs through very large sand filters. The heavy metals would show in my regular water tests and soil tests of the farm.

Pools are chemical soup to start with. I use as basic elements as I can.

calcium chloride: hardness

sodium bicarbonate: alkalinity

sodium bisulfate: ph down

calcium hypochloride: chlorine