Fibreglass swimming pool

Hello fellow laminators!
I have just finished re fiberglassing an old pool.
I sanded down 3 topcoats,to the fiber.
Applyed 450gr.mat.
Made my own filler and even d out the irregularities.
applyed a 60gr.tissue.
Sanded and gave it a topcoat.
7 days later the pool was filled.
2 days later,it was full,salt was added and the pool heater turned on.
2 days later,brown spots start appearing on the pool floor,not on the walls,with a slight smell of styrene in the room,its an indoor pool.
Now,15 days since the pool was filled,or 21 days after the topcoat was applyed ,its the same smell and the same stains.
What is this?
Gratefull for any help.

 

Depending on a few things like the exact gel coat used, the catalyst and the % of it, ambient temperature, ventilation, color of gel coat, how it was applied (rolled or sprayed) and a few other things, there could be a couple of reasons.

Its most likely the cobalt reacting with the water chemistry, this can leave an uneven dark shading on the surface of the gel coat and it can happen rather soon after its filled. I was told cobalt and chlorine form cobalt chloride in the right circumstances and it’s the same dark stain you see by blistered on boats and pools, I’m not sure how accurate that is though.

The quick fix is to get some oxalic acid, you can find it by that name, or it can be relabeled as a cleaner for rust and other stains. The recommended method is to lower the PH, add the Oxalic acid, let it sit until the stains are gone, then adjust the PH back to where it should be. This should take about a day or so to complete. I normally try it without lowering the PH first, if it goes away you saved time and money, if they don’t go away then lower it.

I was a plant manager at a F/G swimming pool company for about 20 years, I also had my own company renovating swimming pool for about 10 years.