I have a 25,000 plaster pool with attached spa. This year since opening I can't get much of a free chlorine reading. I use the bio guard test kit but I did just buy the Taylor 2600. If the free cl test sat, it would eventually get fairly pink. The guy at the pool store told me just to walk away from the test and come back in 15 minutes. After doing some research I think I have a high combined chlorine. I shock with 5 gallons of liquid shock Monday night. Tuesday am I was registering adequate free but by the afternoon it was low again. The test at the pool store showed .5 free chlorine, and 2.5 total chlorine. It is calling for me to add nine bags of burnout 73. My cya is 35. Everything else is good. The water is clear but the hot tub does smell when it's running. Advice?