It is now a year since I last posted in this thread but, for continuity, I am bumping the thread to provide an update, rather than open a new one. Last year I converted from Bromine to Chlorine without draining any water and without attempting to somehow allow for or compensate for the residual bromine in the pool. I was prepared to drain the pool if required but thought I'd try using chlorine first, managing the pool as if it had no bromine in it. At the end of last year I was using chlorine pucks because I had initially had some problems handling the liquid chlorine, spilling it on myself and generally making a mess. The pool was clean and free of algae at the end of the year but, as you can see from the later posts, there were concerns with the potential buildup of CYA from the use of the pucks. Advice here was that the use of pucks would require backwashing unworkably large amounts of water on a regular basis so, when I opened the pool this year, I decided to retry liquid chlorine. Over the winter, while in Florida, I acquired a TF-100 test kit so I was better able to test the water to see what was happening. When opening, I ignored any residual bromine in the water, managing as though it was a chlorine pool. When the cover came off the pool the water was dirty so I shocked it using the SLAMM instructions on this site, adding no algaecide. In a few days the pool was clean and showing no overnight FC loss and I made the required adjustments to pH using muriatic acid and to pH by adding baking soda. CYA was already at 50 ppm from last year so I just went with it, adding about 3 litres of liquid chlorine a day to maintain the FC at about 3 ppm. I'm very pleased with the results as my pool has never been as clean and sparking as it now is. I have not shocked the pool even once as it hasn't needed it and the water has been very stable.
My conclusion here, for the benefit of those with bromine pools wanting to convert, is that the conversion is easy; don't get hung up on the bromine issue. Just pretend there's no bromine in your pool and proceed with the instructions on this site for managing with liquid chlorine. I can't say that there is no difference between this approach and a fresh fill, only that it's easy to get good results without a fresh fill. One thing I found was that I needed a lot of chlorine to reach and maintain the recommended 4-6 ppm FC with 50 ppm CYA but I also found, with experimentation, that I didn't need that high a level to maintain clean water and no CC. I now keep it between 2 and 3 ppm with perfect results. Liquid chlorine costs a little more than using pucks and I am using more chlorine than I thought I'd need. I pay $6 for 10 litres of 12% chlorine and I use 3 litres a day so it's costing me $50 to $60 per month. I haven't found any cheaper source than this around here. Pucks would be about $30 a month but I'd be using more water and there is a cost to that. In any case, what I'm doing is still a lot cheaper than what I was doing before, spending a fortune on bromine tabs, algaecide and pool store baking soda at twice the grocery store price.
For the record, my water tested this morning as follows:
FC 2 ppm (forgot to add chlorine last night as I usually do)
CC 0 ppm
TA 110 ppm
ph 7.8
CYA 50 ppm
Hope this helps anyone out there who is tired of spending a fortune on bromine and wants to convert to chlorine as recommended on this site.
ps I switched my hot tub to chlorine as well and it is pristine, much nicer than with the bromine tabs in the floater. There is no odor at all, something I never achieved with the bromine tabs.