Quote Originally Posted by waterbear
What you have is dichlor and trichlor, both are stabilized chlorine and using them will cause your CYA(stabilzier) levels to rise. It would be fine to use them now instead of buying stablizer and then when you CYA is 30-50 ppm switch to bleach. Be aware that the trichlor tabs are acidic and can lower your pH...use borax to raise it if this happens. the dichlor doesn't have much impact on pH and would be good to use as shock (if it is in granular form) right now since it dissovles quickly and will help get your CYA levels up. Just keep close tabs on your CYA.
I agree with about 99% of Evan's comment. One-point of disagreement: Di-Chlor WILL lower your pH, just not as drastically or dramatically as Tri-Chlor, but it will most definitely lower it. That's my personal experience as recently as late April/early May. I used leftover Di-Chlor when opening and had pH drop. No big deal--a box or two of Borax fixed it. But pH dropped. (needed CYA, too).

As long as you need CYA and you pH isn't too low, there is absolutely NOTHING wrong with using up your Tri-Chlor tabs and Di-Chlor powder. If you follow our general advice to test chlorine and pH everyday or every other day, and once a week test T/A and CYA, you'll know EXACTLY when to stop using the pucks and powder and switch to bleach. Plus you won't have to spend MORE $$$ on CYA.

You've spent the money, use them up, but use them wisely and you will have NO problems. Test, test, test!