Absent bald spots, the answer of this question relies more on when you want to improve the aesthetics of your pool.
“Bald spots”, where you can see the surface underneath indicate a problem that needs to be addressed immediately. While your pool’s surface is not responsible for the structural integrity of your pool, it is responsible for sealing it.
- In concrete pools, which are typically resurfaced with marcite, plaster or white coat, bald spots are identified by abscess in your surface. The shotcrete or gunnite can be seen underneath these bald spots. There is usually a sharp difference in color between the white of your pools surface and the concrete underneath. Water can easily permeate the shotcrete or gunnite of your pool eventually making its way through your pool's shell damaging it in the process.
- In fiberglass pools a surface failure or “delamination” will look like quarter to dollar sized pot holes that are only a few mm deep. They usually have jagged edges. The cause of these delaminations are usually age or poor water chemistry. Once one delamination appears, more follow. Resurfacing immediately upon noticing the first delamination may save you money, as they require a lot of work to pull off and grind out.
Absent bald spots, concrete pools can suffer from aesthetic flaws that come up as the pool ages. The flaws include etching, pitting and stains. Removal of these flaws may require that you resurface your pool to remove them. These are not damaging to your pool and can be handled at your convenience. If the pool is part of a commercial attraction best practice is to stay on top of these issues as they arise.
Fiberglass pools often do not suffer from the type of pitting or etching or staining that concrete pools do. Stains are often easily removed from fiberglass as its non-porous. The non-porous nature of fiberglass allows you to remove stains with the proper chemicals and a vinyl brush. This alleviates the need to resurface.
Fibre Tech can be applied on concrete pools, giving you the best of both worlds when you go to resurface. It is non porous making it highly stain resistant. This seals your concrete so you do not have to worry about etching in the future.