Time to replace sand?

[jonno]

I couldn't test within 2 hours of sunrise because we had a major storm - almost an inch of rain (desparately needed).
9am numbers:
FC 21 (-4.5 drop over 13 overnight hours - could some of this be dilution from the rain water?)
CC 0.5 (yay!)
pH 7.2 - Since the FC is higher than 15, this is falsely high, so I'm hesitant to add any more m. acid until I can lower the FC below 15.
TA 170 - Probably not a good reading due to high FC - it turned from green to blue at 140, light orange at 160, orangey-reddish at 170
More storms and rain today, but I'll keep topping off the chlorine level to 25 throughout and see how the FC holds tonight.

My pool is an unbelievable transformation - thanks to Ben, forum moderators, and the community. Ben - Have you considered starting an area for posts of appreciation and success stories? Perhaps under the group Ben's Corner, Water Treatment Testing and Problems, or even Odds and Ends. Such an area would be encouragement for people with big problems to know that the POPP is worth it. My path from swamp to crystal clear water covers eight pages of posts - but if there were a Success StoryArea, I would condense it to a single post with a few before and after photos and put in a link to this thread for anyone who wants details.