Waterline tiles which are the band of tiles below the coping tiles are generally glass mosaic tiles. These tiles are laid directly to the walls of the concrete pool. We recommend a minimum 250mm strip of waterline tiles so that the tiles are below the pool skimmer box and so always submerged in water. We use and recommend Ezzari Spanish glass tiles. The benefit of waterline tiles is both asthetic and also prevents from discolouration or ring stain.