I use a product called Billy Doo which is an epoxy type adhesive which can be used to restick the small tiles back on withouthout draining the pool, I just cant figure out why the tiles are comng off. I have just bought(January) the house in spain which is six years old and everything was great until the last two months . I am getting patches of two and four tiles coming away in various parts of the poo and cant figure out why. The Bily Doo is great but costs 14 euros a pack and only does about 10 -12 small glass tiles. Any advice would be appreciated. I thnk the company is called bzc.co.uk if that helps anyone. Brilliant stuff, cures underwater in less than 24hrs, but be quick applying it.