New to the forum

On a Sylvan IGP [~24k gal] from the mid 1980's we continue to have tile that pops off with residual loose concrete. I've replaced a great deal of the tile but it happens again. When tapping on some of the coping it sounds as if it's hollow which tells me that perhaps the coping bed has been eroded allowing water to freeze / thaw and pop the tile?? Is this correct? plausible? make sense? The coping is a bull-nosed open-faced rough concrete aggregate in about 2 ft lengths and mortar is used to fill the joint between the coping stones as well. The current plan is to use a chisel and carefully remove the coping and re-mortar in place and reseal the gap at the decking. The question is about the mortar. Is there a special type to use specifically for pool coping? Will any Quickcrete mortar mix do the job? is this truly a DIY job or should I be looking for a contractor? Any insight would be greatly appreciated!!

sorry for the lengthy description but wanted to provide as many details as possible.


thank you
Rob