Gunite swimming pools can be particularly susceptible to surface staining and damage. A professional refinishing and painting process can go a long way in preventing these issues from becoming severe and unsightly.
Things You'll Need
Protective plastic suit
Concrete patch kit/Plaster
Pool epoxy/concrete paint
Small and large rollers
Textured roller covers
3-inch brush for cutting in (if needed)
Drain the pool using your submersible pump first. Make sure you have a plan in place to ensure you don't create a flash flood in your own backyard. Check with local codes, and direct the flow toward a nearby storm drain or sewer if you can. Remove as much water as you can. Use the leaf blower for any excess moisture, and wait for the whole surface to be completely dry to the touch before proceeding to the next step.
Wait for a sunny day if your pool is an outdoor one and avoid windy conditions if you can. Suit up in your protective gear and get all your chemicals together. Start by spreading soda ash around the floor drain and covering or removing any jet housings around the pool as well. Mix together some muriatic acid and water in the garden sprayer. It should be a 50/50 or more concentrated mix. As you spray the pool's surface one section at a time, work in the mixture with the wire brush for particularly stained areas and the regular scrub brush for other spots. Do this across the entire pool area. If there is a good amount of scum and dirt build up, sweep or vacuum the area before going on to the next step.
Spray down the pool with water, and create a new mixture of tri-sodium-phosphate (TSP) in a bucket. Use a scrub brush to wash the entire pool with this solution. This will help neutralize any remaining acid and remove lingering dirt and grease. Once the whole area is completely washed, rinse it again with some water and let it dry.
Look for any cracks, divots, or other damage to the surface and repair them with the concrete patch kit. When buying the patch kit, make sure to read the directions on the product to be sure it matches up with what your pool is made of. Don't bother with tiny hairline cracks, as you will be able to cover those with paint.
Get your brush, rollers, paint, and five-gallon bucket together. Masonry waterproofing paint such as the "Drylok" EXTREME brand is a great option, but there is also a specific paint designed for providing the ultimate protection for your pool. Ramuc EP Hi Build Epoxy promises up to eight or more years of service life and is literally made for pools.
Tape off all areas you don't want to paint, and start cutting the pool in with the brush, working your way around the top rim. Every pool is different, and if your pool allows you may not need to cut in at all. You can tape off the top of the pool or just use a small roller for cutting in. It's up to you and dependent on the conditions you're facing.
Roll the rest of the pool out using a thoroughly soaked roller. Work from top to bottom and from the deep end to the shallow end. Watch for big drips on the walls, and leave the pool floor for last. Paint yourself into the corner by the stairs and finish up there.
Wait at least five days before refilling the pool, and keep out any excess water or debris with a giant tarp or your leaf blower. Try to paint when the week ahead is going to be nice and sunny. If it does rain, remove the surface water as soon as possible to make sure the paint is able to really cure before refilling.