The Cl evap thing is kind of a myth... Chloramine is what they're using now, and the levels needed to harm plants would harm YOU too, lol! Go ahead and use it for your flushing as-is.
Use the rain water like RO: Add CalMag and bring it to 300ppm. Then add your base nutes- Start at half the recommended dosage, and keep your total ppm around 800 to start. Then pH to your coco range.
You're going to be using rain or RO a lot I'll bet, so this is the time to start learning how it works, and testing to see how high you can take the total ppms without tip-burn.
stinkyattic Reviewed by stinkyattic on . Lockout- Hard water, rain water, choices! OK I'm officially back and man do I need help! We moved last year and ran into so many problems with my new setup but ironed most of the kinks out. As usual with a new setup and strain there is a learning curve as you relize mistakes and stabilize the problem. I have narrowed it down and have discoved it to be the water. So I'll tell you everything I know about my water source. It's well water, we live near a large lake that isn't the healthiest, but not biohazardous yet. The pH is at Rating: 5