Coraasan provides the water here in Sajoma. Pumped out of a local river when the water is clear enough. The rains are messing with that. I don't think Coraasan treats the water with chlorine. Occasionally I will add some based on the amount I see we've gotten in the cistern and a chart I have. Is that worth it? Chlorine is a pretty volatile chemical and the surface area of the cistern is a pretty large. Just wondered what others do and if I'm wasting my time.