Hello from MO! I appreciate this site, and have visited several times over the years to get pointers. I've officially stopped "winging it" with test strips and bought a real Taylor k2006 fas-dpd while the pool is completely draining. I know the water can recover in a week or so by following guides here, but the family is impatient. This last month the pool has been perfect clear until a week ago when some cousins swam. After that she went cloudy to green in a couple of days. I elevated shock with 12.5% I get from a buddy's business, up over 10% FC, and that usually clears quick. Not this time though. Been over 10ppm for 5 days and green. I tried some metal product, in case it happened to be copper, but no. Thankfully the last few days have been in the 60s.
But, with 90s pressing back, we want clear water, hence the refill. Now I realize that knowing exact CYA and exact FC is important. So hopefully clear waters from here out.
I also cleaned the sand filter out per the directions and videos here. I have some cellulose fibers now too.
Once she's drained, I'll get the last bit with a shop vac, scrub and clean, then start refilling.