This is the 3rd season since we've had our inground pool installed.
We have an SWG but once or twice a year have had cloudy water without any combined chlorine and chlorine has always held overnight first time, so I'm not even certain I had algae. Each time I've treated as algae with the shock as prescribed on this forum.

Additionally once or twice a year, I've noticed water behind the liner in exactly the same spot. It forms in the deep end where the sloped side wall rounds out to the flat bottom of the pool. The location may not be significant as this maybe the deepest part of the pool and the water simply runs to this point before draining.

Each of the three years in early August, both cloudy water and water behind the liner occurred simultaneously and correspondingly disappear around the same time. The first year we had an incredible rain storm where the water went as high as the coping, so I thought the water could have went over top of liner.

Right now its also occuring now. The water is to cold to swim, but after shocking to treat the cloudy water as algae, I noticed the vacuum stalling over the spot in the pool where the water has previously formed behind the liner and the pressure on the filter drops. Turns out liner was being sucked into the vacuum opening and restricting the flow. I can feel the water behind the liner by dragging the end of the broom down the wall across the spot and onto the floor.

I'm wondering if there is a relationship between cloudy water, and water behind the liner?

Is it possible that one causes the other, or they have both have the same common cause.

Anyone have any ideas?