06/21/2026
Terry’s Pool Tip of the Day, regarding stains from metals & shock treatments:
When shocking the pool you can have some reactions occasionally.
The plaster can suddenly develop stains immediately afterwards,
Sometimes you can clear it up by throwing
Bicarbonate on top of the darkened area,
Calcium Carbonate can fall out of solution after adding cal hypo shock,
The most common is copper & iron reaction with the shock.
Which can stain in a dark color ( copper ) or light brown or yellow on the plaster ( iron ).