If rainwater is the one sort of water available you then will want to use it. Apart from the obvious such things as keeping your gutters clear and warding off spraying near the home or if the wind is against the home which you could add a rainwater conditioner. This will add the salts that rainwater doesn’t have. It will also neutralise some but not all of the feasible contaminants. Mains WaterIf you’re in a local with Chlorinated water, a water conditioner will put off the Chlorine. In areras which use Chloramine, ther conditioner will still work, but needs to be used at up to 5 times the traditional rate.