Keith,

You can use the "how to test if . . ." link to get an explanation of how you can 'extend' your CYA test to cover the higher range.

Then, use the "Best Guess" page to find the right chlorine range . . . and you should be good to go.

Of course, you'll need to switch to either calcium hypochlorite or bleach (sodium hypochlorite) as your primary source of chlorine.

You can give away, or seal up, your stabilized chlorine. You might want to hang on to it long enough to see how fast your CYA drops (no need to test more than 2x per month). If it looks like it will take more than a year to get below 100ppm, you'd better give it away. Old chlorine tabs and powder tends to give off a variety of noxious fumes that aren't good for you and are TERRIBLE for wiring in your garage or storage shed.

Ben