Heh! Two days ago you were intimidated by the testing process and now you want to test rain water. It happens to all of us, that desire to test any and all water sources . Before long, you'll find yourself taking the test kit along when you go to friends' pools, to public pools, to motel pools (and you'll probably not want to get into those . . . ).

One thing you do want to test is your fill water so you know how much chlorine, TA, and calcium you start out with when you have to top off your water.

Record keeping is essential. I used to keep a notebook in the pool house; now I record test results and make notes on the iPad. Knowing the 'clean' pressure of your pump/filter is good info to have, right after cleaning the system or backwashing it. You can see trends at a glance and yes, it totally helps you be proactive.

I'm glad you find the PoolCalc helpful. Next to my WallWhale brush it's my favorite pool tool.