First of all, I would like to thank this forum for all the good information that I have found here. Perhaps the most important thing, was to buy a GOOD tester to keep track of your pool's chemistry. I had been having an issue with mustard algae, probably because of a very high CYA level and not having enough available chlorine. I dumped about half of the water out and got my CYA level down to about 60. (I didn't have the new test kit before I dumped the water but I imagine it was around 120) The pool is 30 years old and had never been emptied. Most of those years, trichlor tablets were used.

After reading about the popularity of using bleach, I thought I would try it. Here is my experience. I started keeping rather detailed records of the water's chemistry, checked the chlorine, combined chlorine, ph, and water temp. every day. Checked the total alkalinity, calcium hardness, cya, sat. index every month.

I am trying to keep my chlorine level between 5 - 10 ppm & ph 7.6 - 7.8. given my numbers:
15,000 gal in ground pool fiberglass walls/gunite bottom. 1.5 hp pump running 9 hours per day (4 hour break in the afternoon). Water sparkling, no algae, bottom plaster flaking off, needs to be redone.

Total Alk. 110 / Ca hard. 190 / CYA 60 / Sat. Index +0.2 / water temp 82f - 90f (depending date & time of day.

When using bleach, I was using about nine 96oz bottles per week to maintain a good level. I used bleach for over one month. After some mental math, I felt something was wrong, so I switched back to tri chlor tablets and continued keeping detailed records. I found that I was using four tablets per week. Here is a break down on weekly costs:

(9) 96oz bottles = $13.50 / (4) tablets = $6.72

This is based on an average price of $1.50 per bottle of bleach (has gone up in the past few weeks)
Tablets cost $1.168 each. (based on 40lb bucket @ $90 / each tablet weighs 8.3oz - 77 tablets in bucket - calculated)

I also calculated the amount of tablets (in oz.) used by weighing the remainder of each tablet, every morning at the same time. The chlorine level dropped slightly as the tablet grew smaller in size. (this could be eliminated by replacing the two tablets on different days)

My impression of using bleach was:
I was having to cart a lot of bottles every week from the store and using up a lot of space to my trash can every week. (we currently don't have a recycling program here) The weekly transporting and storage was a pain.

My chlorine level was varying between 3.5 - 10 and was having trouble keeping it a stable level (especially during the day)

I started using a lot of acid to maintain a proper ph. I presume from the use of the bleach. (according to the booklet in the test kit)

Although all the bleach purchased was "6%" I suspect some purchased from Target, may have been lower or perhaps old because of the small amount it raised my chlorine level. Not impressed by the quality control of bleach.

After I switched back to the tablets:
I only went out twice a week to drop 2 tablets into my skimmers instead of more than one a day with bleach.

My chlorine level became very stable (7.5 - 8.5ppm)

I stopped having to use acid ( 7.7ph stable over the last week) Saved money on acid, as well as the hassle of dealing with the stuff.

I'm not trying to start an argument about the virtues of bleach, just wondering if I am missing something (or doing something wrong) in the "bigger picture?"

Thanks again for the good information.