cin

Hi Chem Geek, Thanks for the help! What you say makes a lot of sense, but if I put much more chlorine in at once the levels will go above 10ppm. Too corrosive for bathing. As it is now, I test the water 3 times a day, and add chlorine as needed (twice a day at least). I add enough to bring it up to 9ppm or so in the morning and before bed, so that it's usable during the day, and that it doesn't go down to 0 at night. I was under the impression that I'd be able to stabilize the chem situation so that I only need to add chlorine once every 2 days or so. But what you are suggesting is that my bather load is just too heavy for that, and that with that load I will have to constantly add chlorine. Which is fine, as long as it "normal". So my plan now, given your clarifications, is to continue tweaking the chlorine level to 9ppm in the morning (to make it usable during the day) but increase the amount I put in at night. It'll be above 10ppm at night, but then there should be some left in the morning, after it has oxidized the nightly bather load. Does that sound right? Thanks a bunch!!

Hi all, I just got a small (216 gallons, 818L) new hot tub, and after letting the chlorine go to 0 for a few days on the original fill (by accident), I ended up here reading all about proper water chemistry. So I drained the tub after shocking it to 10ppm a bunch of times (Chlorine was disappearing fast, pH was drifting up all the time, I had added too much Calcium Chloride and TA) and started over, following the instructions of Nitro's posts: - Filled the tub with hot tap water (Vancouver BC, best tap water in the world, perfect ph) - Tested it, used the Pool Calculator to estimate quantities - Added 53ml of Calcium Chloride (water was at 50-80 ppm) - Added 26ml of baking soda to up the TA (was at 60 ppm or so) - Added 361ml of Borax - Balanced the pH (it was WAY up, like off the chart at 10) with pH- dry acid and also increased the CH as it had gone back down to 50-80 ppm (I blame the Borax) - Aerated the water for 15min - Balanced the water again, to 7.4 - Added 7ml of Cal-Hypo chlorine at 47% - Tested the water (using strips and a pH/Cl rainbow drop test) At this point the chlorine was at about 9ppm and everything else was perfect. Waited a bit then 3 clean bathers with swim suits got in for an hour and a half Tested the water again and the chlorine had gone down to about 3ppm. So I added a few more ml, to bring it back to about 9ppm. The morning after the chlorine had completely disappeared. CH and TA were also down again, so I topped that up a little. Perfect pH. So I added 7ml of chlorine granules and went to work. When I got back the chlorine had disappeared. So I added some more. We've been using the tub, the water is fantastically clear, but I am constantly adding chlorine as it gets eaten really quick. I'm adding chlorine twice a day at this point. The CH also seems to keep drifting down, which I wasn't expecting. I read about Chlorine Demand and all but I'm not sure I understand why our tub is eating so much chlorine. The tub is about a week old, the filter is clean, the water is 2 days old. Could it be because of the small volume of water combined with 3 avid bathers, and possibly the rain? Or should I conclude there's something in there eating the chlorine, and I need to decontaminate the tub even though it's so new and clean? (something that may have settled in when I let the chlorine fall to 0 in the first few days?) Any idea why the CH is drifting down? Thanks! (curses, my carriage returns are not showing proper)