Hi! I have had a pool since 2003, and have been taking care of my parents' pool since the late 80's, and for all those years, I have been using the same "tried, tested and true" method to open and maintain my pool, as thought by my uncle, who has a pool since the late 60's, which seems to go roughly along your guidelines, except that I use a cheap OTO/PH test kit that came with the pool. The only products going in my pool since the early 90's are HTH calcium hypochlorite, CYA, baking soda and PH- powder.
At the start of the season, I would dump 4 pounds of calcium hypochlorite that I have pre-mixed with hot water in a bucket, and maintain the chlorine in the "orange" range until water clears, which I assume is roughly what you call SLAMing the pool.
After 2-3 days, when the water is clear, I would let the chlorine drop to 3 ppm, maintain that level and adjust my pH between 7.4 and 7.8. After a week or so, I would add 3.5 pounds of CYA, and I usually would add another pound by late July to mid-august and my water would stay clear for the whole summer, even in the warmest days of July and August. I check daily my pH and chlorine with an OTO kit, but once a week or so, I use sticks to check for FC.
But for the last 3-4 years, it's taking longer and longer after the initial shock to get sparkling clear water, especially this season. After 4 days, my water was still very milky and I couldn't see more than about 2 feet deep, and after a full week it was still cloudy. I got the problem "solved by using alum, but I feel I shouldn't have had to.
I have been busier than usual the last 2 weeks so I forgot to add more CYA, and earlier this week I noticed that the usual half cup a day wasn't enough anymore to keep my TC at 3 ppm, even though it was still sparkling clear, with no visible algae, not even behind the ladder. So I checked my CC with a stick and it showed 0, so I dumped a full 2 cups of calcium hypochlorite in the skimmer to boost it up and on my way to work I bought some CYA, but when I came home that night my sparkling clear pool turned from crystal clear to a pool of milk.
Obviously I am doing something wrong, but could someone please tell me what it is, and why did it work for 20+ years without any issue? My pump runs 24/7 from the moment the pipes are connected and my pool is filled all the way until closing time.
Thanks for reading,