When I first started out with CPs, I used filtered water (the ones for drinking), but after that I changed to my current system, which is:
1. Collect rain water in a big pail (almost like a garbage bin) and use that.
2. If during summer I run out of rainwater, I just fill the same container with tap water and let sit for 1 day (to dechlorinate), then use that to water.
3. If it rains, then no need to water at all.
Like now always raining. In fact if it rains everyday, my alternate activity instead of watering is to empty the water trays so that the plants are not too wet all the time.
4. If it is really dry and I don't have time or do not have enough water anymore in my bin, I use straight tap water with a garden hose.
But during summer, almost all the time I usually use aged (dechlorinated water).
During Rainy season, almost all the time I rely on rain or rainwater.
TTFN
Arvin