I thought I had this TFP method figured out...
Long story short: Opened my pool 2 weekends ago. Water was slightly cloudy (couldn't quite read 'Hayward' on my main drain, 8 feet down). FC 0, CC 0. Dosed to 6 ppm, lost 4 ppm within an hour.
Started SLAM procedure -- lowered pH to 7.2, began dosing to 20 ppm FC with CYA showing 40 ppm.
All was going well, pool cleared up nicely. And it's still beautifully clear.
Problem I'm having is this: I can test after work and show 14.5 FC, then dose to my target level (in this case, 24 FC to carry me over until the next morning). Testing 2 hours later (right before bed...), test will show 30+ FC.
Sometimes the opposite will be true. I'll test and dose accordingly, then 2 hours later see FC only slightly higher than the previous test. Dose again, test 2 hours later, then have obscenely high FC.
The only thing I can think is that I'm using an XL Option I purchased late last summer but never opened. Is there any chance the DPD powder has "gone bad"? It was stored inside (in our guest bedroom) all winter, along with the rest of my TF100.
I'm keeping a fairly detailed log of tests, doses, etc. and can post same if need be.
Thanks in advance, folks. This is just driving me nuts!