Phil8bnz

This was an old post but I had same problem last week a thick waxy yellow scum line in our spa. We use slow dissolve bromine tablets. The water was getting very fizzy and I suspect it was due to my latest shock dose of chlorine reacting with the bromine, and that the water hadn’t been changed for a few months - but I’m not a chemistry expert. I recently read that chlorine and bromine don’t mix well The spa shop said to use an oxidising granule instead of chlorine granules for the shock doses. So I’ll try that this week. Have changed the water now anyway. I’m hoping that yellow scum hasn’t coated the insides off the pipe work and thermal components.