A common and very effective method of purifying swimming pools is to use electronically produced copper and silver ions. It was previously promoted that copper was the more efficient algicide and silver the more effective bactericide. More recent studies have shown each to be highly effective in the control and killing of both bacteria and algae. Together they give superior results.
This method has the advantage over chlorine of remaining very stable in swimming pools. The pool will stay sanitized for days or weeks with the system turned off and no additional copper or silver being added.
Copper and silver are not absorbed through the skin, therefore , are not carried out of the pool by swimmers. They are also not affected by sunlight and actually become slightly more effective as the water is heated or the pH increases.
Copper and silver are safe. At the normal recommended levels of copper in a swimming pool, a person would have to drink over two gallons of pool water to get the amount of copper in one vitamin pill. A glass of EPA approved tap water could have five times as much copper in it as a glass of swimming pool water. The tap water could also have five times as much silver as a glass of pool water.
The Environmental Protection Agency completely removed any limits on silver in drinking water in 1989 because they said it presented no hazard to human health.