Thanks guys. My liner installer is a good guy. But as you might expect, he, and I am guessing the manufacturer as well, considers 12 FC (my shock level at 35-40 CYA) to be insane. This is what I would anticipate to hear from all these guys. I am sure any literature / guidelines they give me will refer to 1.5 FC levels. I also already had the "be careful what you read online" speach when I reference info from here. So I have this problem of credibility and who's credentials matter. I am sure I have maintained my pool to the TFP guidelines, however what liner manufacturer believes these are correct? I am 100% positive I will be told that 12FC is way too high at any time and that is the cause. I doubt a link to TFP will convince anyone either. I guess I will find out in the spring when they come to look.
I think I will put a sample in plain water in the meantime, good suggestion.
Intuitively, I have to say it "feels" like this is chlorince related, even though I know you will tell me about 100's of people using TFP / BBB method that have no issues.
My installer, who I think is trust-worthy, claims this manufacturer to be the best in the market, and that he has not had any fading issues yet (for the past 5 years).
Before you ask, I check my FC daily / every other day at least, my PH 2-3 times a week, and my CYA as needed, 3-4 times per summer. I am pretty anal about it too.
I have 30-40 CYA, target 3-5 FC and my PH is always within range, has never been lower than 7.2, since I have owned the pool.
Thanks.