Hempy is a good reason to use clean water. Bleach has a pH between 11 and 13 and that's why I never use it in rainwater. Don't worry if you have a little natural ppm in the Rainwater. It doesn't hurt anything and is natural ppm. If you run a RO system from your water lines and get 7 ppm water, you can mix it with 40 ppm Rainwater-RO mix 50/50. One has a lot of "ppm room" with water that is in the 30s or 40s ppm. . Don't be concerned too much with natural ppm unless it's chloride, sodium, or hydroxyl content. In rainwater natural Spring ppm is mostly pH neutral and won't affect the soil pH long term.