It depends on the type of adhesive that is being used. If an epoxy-based adhesive is being used, then it is possible to replace the tiles without draining the pool. However, if a cement-based adhesive is being used, then it is necessary to drain the pool in order to replace the tiles.

It depends on the type of tile you are using. If you are using a mortar-based adhesive, then you will need to drain the pool in order to apply the adhesive (and then re-fill the pool). If you are using a strong epoxy adhesive, then it is possible to do the repair without draining the pool. In either case, it is important to properly prep the surface before installing new tile.