I also freaked out about the quality of my water and was thinking about the exact same thing, "How do I cheaplly filter my tap water?" Rocketman hit the nail on the head. See if you can get a report online about what is in your tap water. I found mine after googling for about 10 minutes. I wasn't worried so much about chlorine as I was about CHLORAMINE, which can't be evaporated out. After seeing the report I realized that I didn't need to do anything special with my water. That being said...
I bought a big rubbermaid container and put an air stone in it. I like to keep it half way full and every time i water I top it off and leave it open for a night. If the air stone does anything it helps evaporate chlorine, but more importantly oxygenates and aerates your water. I hand water in hempy buckets and use GH FloraNova nutes. My tap water ppm is 200-230 and ph is 7.1. I haven't had any problems.
Also, I never have any Cal or Mag issues. A lot of people who use RO water have to supplement this. If you can use your tap water it will save your a lot of time and money in the long run. If your a serious hydro/aero grower, then I can see the need for RO. Otherwise, if you can use your tap water just by letting it sit out overnight thank the green gods! JMHO.