I'm relatively new to pool maintenance, inheriting an existing pool with our current property in Dec 2015.
My sincere thanks to this forum for setting out the FCL/CYA relationship. I had been using multi-function tabs exclusively since the start of the season and my CYA hit 70+, at which point algae started to take hold. Having stopped the multi-function tabs (now using liquid chlorine), shocking and then changing about 1/3 water volume (CYA now ~40), my water is now in better shape - thanks again.
Slight digression aside, I'm after some advice on the structural side of the pool.
Essentially, around almost the entire perimeter of the pool there is a gap between the vinyl liner and the (bullnosed) coping stones. From inspection, I can see that the gap has variably been filled with i) mortar, ii) silicon, and iii) some form of rubberised sealant. I've attached some photos below.
I'm pretty sure that there's not supposed to be a gap here, as effectively water can leak under the coping stones and potentially behind the vinyl liner - bad on both counts. As we head towards winter, I'm feeling the need to do something about it, so broadly my questions are:
1) What is the preferred material for repairing the gap?
2) Any installation tips?
Thanks in advance