1. Softened water is not bad for plants. (Who told you that?)

2. Softeners don't remove chlorine. Carbon filters do, but may become dangerously contaminated with bacteria as a result. Some manufacturers add silver, in various forms, to try to prevent this from happening.

3. If you are collecting rain water using downspouts . . . depending on the area, you may get a significant burst of avian feces (bird crap) added to the water. If you have a rain after several weeks of no rain, the contamination may be especially heavy. Your pool filter + chlorine + TIME can clean this up, but you'd need to add the rain water via the skimmer so the added water goes through the filter before it goes to the pool (to remove particles). And, you'd need to be sure you have adequate chlorine (per the Best Guess chart). Finally, you'd need to wait 12 hours after adding the water, before swimming.

Using small amounts of polyquat in your rain water, as you collect it will (a) help sanitize it and (b) make chlorine-resistant amoebic parasites easier to filter out. (Polyquat will NOT kill these.)