North side pool services

Fiberglass Pool Has Black Spots?

So you have recently relined your swimming pool, it looks amazing but a few days or weeks have past and suddenly you sitting with what looks like blackheads appearing everywhere on your pools new surface!

What is it you may ask? Black spots are the result of a weakened gel coat and the breakdown of the minerals within your fiberglass surface. As your gel coat weakens and the fiberglass breaks down, tiny pinholes will form on its surface, where this sludge-like black substance surfaces.

Cobalt can also cause spots like these.  The gel coat delaminates a bit from the surface and these spots can develop.

Solution

Try to remove them with a vitamin C tablet.  If that doesn’t work, then have your water chemistry tested to see if you have a high phosphate level.  If you do, use a phosphate remover then balance the pool water to see if that solves the problem.