We recently saw someone asking on Houzz if they could get away with having no waterline tiles. Here’s our response:
Hi my name is Dominic from Momentum Pools, I just thought I would provide the following detail and advice. Most swimming pools are fitted with waterline tiles to manage the manage the insoluble, floating veneer of pollen, sunscreen, body oils and fake tan that forms the scum line at the air / water interface. The bath tub ring formed is usually evidenced as a yellowy, brown stain that can be locked into place with a thin film of translucent inorganic calcium scale deposits. Tiles inhibit the formation of this “ring” through the hard impermeable glaze fitted to tiles forming a barrier to which debris cant easily mechanically fix itself to; also the baked, glazed coating is chemically inert and wont chemically bond to any floating compounds etc. The same cant be said , for the typical cementitious linings fitted to pools in place of tiles, they are chemically very reactive and porous in structure with many mechanical fixings points.