Swimming pools eventually need some kind of repair. Some may even develop large holes, whether they're gunite, fiberglass or vinyl. Cracks, chipping and hollow spots can all lead to larger holes. With a little time and attention to detail, you can handle these repairs yourself. Even if you need to call in a professional, it's good to familiarize yourself with the problem and possible solutions before talking to an expert.
There's a good chance the hole is part of a larger crack, so be ready to address both problems. You'll need to actually make cracks and the hole deeper by about 1/2 inch using a 4-inch grinder with a diamond saw blade. The idea is to create uniformity, which will help ensure the integrity of the repair. Wear ear and eye protection during this process. When finished, use a wire brush and shop vacuum to clear away all dust and debris. If the crack or hole goes all the way through, fill it with gunite-grade caulk. If not, use a commercial pool patch and fill the crack and hole. Make sure there are no air pockets in the repair material, smooth everything out and allow it to dry.
Using a hammer and chisel, remove loose plaster. Check for hollow spots by gently tapping the plaster with a hammer. Chisel out any hollow spots, as they are a sign of future problems. Remove all debris with a wire brush and shop vacuum. Use phosphoric acid or trisodium phosphate, available at hardware stores, to clean the area. Neutralize the acidic residue at the bottom of the pool with baking soda, cleaning it up after it's been neutralized. Mix your pool patching material to the manufacturer's recommendation, adding a custom color if you want it to match the rest of your pool. Make sure you match colors to how they'll look when wet. Apply the patch mix with a trowel, using the end of the trowel to force out any air bubbles. Smooth the patch out and allow it to dry according to the manufacturer's recommendation.
Vinyl pool liners are perhaps the easiest to fix. Patch kits are readily available at pool supply stores, and you can even purchase kits that can be used underwater. Cut the patch material into a circle to about 1/2 inch larger than the hole. You don't want to cut a square shape, because the corners are more likely to catch, perhaps causing the patch to peel up. Your patch repair kit will have specific instructions, but the process usually involves thoroughly cleaning the area to be patched, gluing the patch down, and rubbing it to ensure that it seals the hole.
Fiberglass repairs are the most difficult. Getting an exact color match will be next to impossible. Plus, if you have a hole in your fiberglass pool, you are looking at extensive steps for repair, and quite a bit of knowledge. When it comes to holes, loose cracks or extensive spiderwebbing, it's best to call a professional to help you with the problem, as it may indicate a lack of structural support. Any repair you attempt may end up failing.