I had my pool water tested today at a dealer using the BioGuard ALEX system. Here is how it tested:
Total Chlorine: 5.5
Free Chlorine: 2.8
Total Alkalinity: 97
Adjusted Total Alkalinity: 59
Total Hardness: 276
Saturation Index: -0.5
I was told to add the following:
> Total Alkalinity: Add 25.5 lbs of Balance Pak 100 (sodium hydrogen carbonate)
> pH: Add 3.25 lbs of Lo 'N Slo (pH decreaser)
> Chlorine: Add 14 bags of Burn Out 3 (Calcium Hypochlorite - 57.8%) to eliminate the chlorine lock
My in-ground pool is about 23,000 gallons (17' x 32' rectangle, 3' shallow end, 8' deep end, angled corners). I use Doheny 3" chlorinating tabs (99% trichloro-s-triazinetrione), 3-8 oz tabs every 4 days. I also use Doheny Super Shock (Calcium Hypochlorite: 68%) occasionally. I used 2 lbs when I opened the pool 5/26 and 2 more lbs. on 7/1. I run the pool filter about 12 hrs. per day.
The water was a little cloudy when I opened the pool in the spring (5/26). It took a couple days to clear up and since then has remained clear. The 3" tabs, added to the skimmer basket, completely dissolve in 4 days which is why I add them every 4 days. The free chlorine level stays about 3 to 5. I've sometimes waiting a day or two and run the filter without the tabs because the chlorine level has been good, at least I think it is.
I've chatted with a person at Doheny's and found out that the 3" tabs do have stabilizer in them. He said that shocking the pool would not fix the chlorine lock problem. His recommendation was to drain 1/3 to 1/2 of the pool water and refill with fresh water. Then switch to a product with a lower amount of stabilizer.
I know that I can adjust the TA using baking soda and I will probably have to adjust the pH after that, but I'm not sure what to do about the chlorine issue. Can anyone suggest a way to attack the chlorine problem?