Quote Originally Posted by jrv331
Say I want to shock my pool to 15ppm and my FC tests at 5ppm. Would I add 10ppm of chlorine or do you shock with the amount you need and forget about your FC level? Dont want to damage my vinyl liner - its already fading.
John
Yes, add the amount of shock (= to 10ppm) you need. This will bring your FC to 15 or "shocK" level. Shock levels depnd upon your CYA level so check out Ben's Best Guess chart http://www.poolforum.com/pf2/showthread.php?t=365. It is what we use as a guide.

Dave