Sooner or later, the tile in your inground gunite pool will begin to loosen, and fall off. One by One. Every 20 years or so, a complete re-tile of the pool may be necessary. In between, you can do simple, quick repairs to re-affix tiles that have fallen off.
With the use of some simple tools, and some simple cementitious product, small tile repair jobs can be done in a short amount of time. Larger runs of several feet, or entire sides of the pool, can also be done by the pool owner, although more tile repair time and materials will be needed.
Step 1: Remove loose tile with a small flathead screwdriver or chisel. Remove the grout stuck onto the sides of the pieces with small pliers. Also remove, with a small, sharp screwdriver, any old grout that remains stuck to the edge of the tile that remains affixed to the pool wall.
Step 2: Prepare the bed (the wall behind the tile) be removing any loose or flaking material. The video below describes how to build up the bed, if needed, to have a smooth vertical surface that's even with the other tile.
If there are cracks in the beam (the area of the pool wall behind the tile), these should be opened up, and filled with hydraulic cement, pushing the cement as far back as possible into the crack. Pay attention to large cracks in the beam, as these are likely the cause of the tile coming off in the first place. In cases of extreme beam damage, expect your tile repair to only last a year or two, unless and until the larger issues are dealt with. In worst cases, this involves removing the coping stones, and replacing the top portion of the wall - but that is a subject for another blog post.
If the beam area is uneven, with missing chunks of material, these should also be filled in with a pool plaster mix or hydraulic cement (without aggregate), so that we have a smooth base to set the tile against. Important not to build up this area too much, so that your new tile will be even with the tile on either side. Also important if possible, to preserve the "ledge" of plaster at the bottom of the tile. This helps support the tile while the mortar dries.
Step 3:Mix up a small batch of Thin Set Mortar, I use EZ Patch #3, Thin Set for Pool Tile Repair. Wet the area that you will be tiling, before applying the thin set. After mixing to a spreadable consistency, something like Peanut Butter (creamy, not chunky!), use a notched trowel to spread the mix in an even, thin coating. If some drops in the pool, it will dissolve - if not, use the pool brush during clean-up to brush off any clumps.
Spread enough mixture only on the areas that you can reasonably affix the tile within a few minutes. Under 12" at a time. 6x6 tiles are fastest and easiest to set, small mosaic tile, especially if you are placing individual pieces, will take more time. Press the pool tile firmly into the thinset mortar bed, until it squeezes out from behind. Work fast, before the mortar begins to dry. Do this during a cooler part of the day, or fashion some shade if necessary.
After setting the tile pieces, back up to check your previous work, every 10 minutes or so. Tile pieces may begin to slump, or slide down the wall. Without a lot of motion, slowly push and maneuver the tile back into position. For larger tiles that want to fall off, long, vertical pieces of duct tape can be used to help tape the tile in place temporarily.
Step 4: Grout the tile. After the tile has been set in place for 24 hours, you can use a waterproof tile grout to seal all the spaces in between the tile. Thin Set does not work well as grout, I like to use EZ Patch #4, Pool Tile Grout, although, you can use a pool plaster mix as well, like EZ Patch #1.
Use a flexible spreader to push the grout in between the tiles. After it has set up for 10-15 minutes, use some water and gentle hand motion to clean up the extra grout that smeared onto the tiles. After 24 hours, you can use a stiff brush or scrubber to remove the haze and polish the tiles.
Step 5: Fill the pool back up, you're done! Now go brag to your spouse what a handy(wo)man you are!