Not sure if it is algae

Hi
Former long time and regular user of the forum. I have a "rough and dusty" deposit on the vinyl walls. Not the typical mustard slimy algae. Water is clear. (until I brushed it off)
pH 7.4. TC. 5ppm. FC 4.5. CC 0.5. TA 140. cya I keep around 10
Indoor pool with indirect sunlight. Pool covered unless in use.

I brushed the vinyl walls and increased the FC to around 10.
It is going away but with my numbers I was shocked to get it in the first place. Filter always runs 24/7 because it has to. Only use standard bleach.

Endless pool swimming machine.

Any ideas
Andy

Hi Andy, welcome back--I remember you from years past!!

Don't really know what caused the problem, because your numbers look fine, but my first knee-jerk reactions would be to suggest 1) Calcium trying to deposit? 2) Beginning of liner degradation due to a drop in pH around the winter? 3) "Crud" off the cover falling in when opening it?

Janet

New liner.
Recently filled the pool from scratch.
Started about 6 weeks later.
No crud on liner.