I've had this pool for 12 years and it has never gone this long without having some kind of problem. I got the chemistry in balance about the first week in April and it has been crystal clear and problem free ever since. I credit the guidance on this site and the TF100 test kit. Only wish I had found both years ago. I actually enjoy the pool now whereas before I wanted fill the $%&!! thing in and plant a garden.
One thing that really amazes me is how constant the chlorine demand is - I really don't need to test chlorine but about once a week (but I do test every day - and sometimes twice a day) all that is required is to add 3 quarts of 6% chlorine every day. At 5 PM the FC will be 2.5 ppm adding 3 quarts brings the concentration to 4.0 PPM and it will be 3.5 - 4.0 PPM at 8 AM the next day. Then by 5 PM the level will be 2.5 again. It's been that way for two months and does not vary unless it rains all day. The other thing that is different is the filter backwash frequency. I use to backwash about every week or 10 days when the pressure drop would rise about 5 psi. The last time I back washed was either the last week in April or the first week in May - can't remember for sure - but the pressure drop across the filter is only 1 psi above the clean pressure drop after all this time - amazing.
On the recommendation of my local pool store I use to shock the pool with tri-chlor once a week. I would add about 10 lbs at a time. The result would nearly always be a pile of brown debris in front of each filter return nozzle. I assume the brown gunk was dead algae that was too small to be filtered out. Then when I ran the polaris cleaner the brown gunk would be suspended and the water would be murky for several days until it settled to the bottom again. It was a very frustrating cycle and the pool was almost never completely clear. Now all that has changed and when the polaris runs the pool stays clear - amazing.
So THANK YOU TPF for giving me a swimming pool that is a joy to use.