I have had 3 pools and familiar with water chemistry, cleaning, etc. I built a new house in Marco Island in 2016 and used 1 x 1 glass tile on waterline, waterfall, and spa. Over the last year, we have had significant buildup of what we believe to be calcium. We have tried everything to remove the material form the surface including (vinegar, CLR, dilute muriatic) but nothing comes even close to removing this buildup. I was not present when the builder applied the tile (this is my 2nd home) but confident they did not install a waterproofing membrane which i believe to be a significant factor in our current issues. We have decided to replace the current glass tiles and our pool company will be installing a membrane and replacing with new glass tiles. My question, will a membrane significantly reduce this type of buildup? Is there a sealer I can apply to the new glass tiles to reduce the build-up, and lastly - could our problem be a defect in the tile itself? Any thought appreciated!