There's nothing wrong with using tap water, as long as it's city water and not well water. I would not for a second recommend using well water, but I'm assuming you're city treated anyways. Test your water with a PPM meter. If it's anywhere below Id say 200, you're fine. If it's above that, a reverse osmosis filter might be an idea. Bigbux, box temperatures that you're seeing (80 or so) should not be enough to heat stress your plants in my opinion. And typically a box temperature of 80 will mean a res temperature of 72-75, which is totally fine with the right amount of dissolved oxygen. Might want to check your other variables. did you look at them during the beginning of a night cycle or something?
And as for the ducting, these machines typically come with the equipment to duct it out of your room. Go to the BCNL website, and on the video section there is a tutorial to install the ducting. I have that option running out of my room in concert with my AC's hot air venting out as well and it keeps the room very chilly, I love it. My ducting is only about 5 feet on one and about 7 on the other mind you, and they connect into a T before going out. Still does help though, by about 4-5 degrees id say. (my box temp was 85-90 before the AC and hot air ducting, now its about 70).
Ancaps suggestion about water collection is a fantastic idea, and I use it myself for keeping my water levels topped off throughout the week, but I don't collect enough to for actual res changes. For those, I just measure out 35 litres, and leave it out for a day.
By the way, I'm going to be conducting some experiments related to cannabis plants tolerance of chlorine. I've heard from several very reputable places that it's for the most part hype. Hype in the sense that the levels we see in our tap water aren't nearly close to enough to damage the plant. In fact several growers on here use bleach in lieu of hydrogen peroxide to keep their roots white, and I've been told it's a trick used by the commercial hydroponics industry. I'm going to start by not leaving my tap water out, then subbing h2o2 out for bleach if that goes well. It would be nice to have something not quite as 'moody' as h2o2 to keep my res clean.
As for the 2 litres, I find them to bring the water down about 10 degrees over the span of a bout 1.5-2 hours, then slowly back up to where it was over the span of about 4. I find that using this with my air conditioner on extends that 4 hour period to about 8 making it very effective as a suppliment but not a silver bullet on its own. I am currently only using one, but I was experimenting with as much as 3. I was even experimenting with 2 4litre frozen milk jugs, which would bring my temps down as low as 50 degrees, but they leak, and it was way overkill.
