I was visiting Patio Pools and Spas in Tucson, AZ because we are considering remodeling and were looking at their Pebbletec pool. While I was there I checked out the muriatic acid and saw they had the 31% stuff for $9.99 for 2 gallons so I grabbed a couple boxes. Then when an employee came over he asked if I needed any help and so I asked if they sold any liquid chlorine and what was the price and percentage. It was 10% and was something over $11...I think it may have been $11.99 for 2 gallons. So I said no thanks that's a little higher than I like to pay for my chlorine. So he started trying to sell me on it saying it was better than anything I could get anywhere else because they have a local distributor so it maintains it's strength longer. So I said sorry but that's $6 a gallon and I'd rather just buy Walmart bleach that's 8.25% for $3 a gallon. So then he changed direction and said the best thing to use for the lowest cost is the cal-hypo shock bags. He picked up a bag and said it would raise the FC 10ppm for a 16K gallon pool. I looked at the bag and said "My calcium is already on the high side so I don't want to use that because it will continue to raise my calcium hardness". He said it only raises the calcium by a tiny amount and much less than the increase in TDS the bleach I'm using is going to add to the pool. I said I don't think that's true so he kinda got mad and said fine and got quiet to ring me up for the acid purchase.
I kinda wish I knew a little more details to argue my points better. I know enough to maintain my pool but I really haven't researched all the alternatives to know why one thing is better than another. Out of curiosity I went to PoolMath as we were driving home and modeled up an increase of 4ppm FC for my pool using cal-hypo and bleach. I wasn't sure what the cal-hypo percentage was so I modeled it with 53% first and then tried again with 73%. I think they ended up roughly the same for how much extras get added to the pool. I'm typing this from memory but I believe to raise my FC 4ppm the cal-hypo was going to add 2.8ppm of calcium and 4ppm of salt whereas the bleach was going to raise salt by 6.4ppm. I was actually surprised how much bleach increases the salt. So the cal-hypo was increasing TDS by 6.8 while bleach was increasing it by 6.4 unless there are other things inside those products that increase TDS. So it looks like I was right that the bleach was adding less TDS but since the bleach is adding all salt it should be better than increasing the calcium from what I've read.
Besides just sharing the story I'd be interested in hearing how best to respond to these types of conversations and whether any of my conclusions are wrong. I'm also wondering about the steady increase of salt when using bleach. Isn't it eventually going to make water too salty if not using a SWG?