At some point in time if you own a pool you are likely going to find that the tile will start to loosen and eventually begin to fall off. Most of the time tile will last about 20 years before the entire pool will need to be retiled. In between these times there are some simple repairs that you can do in order to reaffix any tiles that have fallen off.
If a tile is loose, you are going to want to take a small flathead screwdriver or a chisel to remove it. You will then want to clean off the grout that is stuck to the pieces of tile. A pair of pliers can usually get the grout off. Once you have cleaned the area where the tile was, removing all the flaking material, you will want to smooth out the surface. If there are any cracks in the wall you will need to fill them using hydraulic cement. Pay attention to these cracks as they are likely the reason that the tiles are starting to fall off.
Use a pool plaster in order to smooth out the base where the tile will be replaced. A thin set mortar can then be used to put the tile for the pool back in place. Once you have placed the tile, clean the area thoroughly.
This type of repair job will only last a couple of years at the most. You will want to make sure to fix broken tiles as they appear in order to keep your pool in good shape. If you do this, you should be able to avoid an entire tile replacement for about 20 years or so. When it becomes too much, you should call in a professional to replace the tiles.