I have white random splotches and spots (resemble water splash markings), and lines in my 3 year old fiberglass pool. There is actually a perfect white faded looking line that goes around the bottom perimeter of the pool along with lines going the width of the pool here and there. At first I thought the color was fading because of these suspicious lines. I contacted the manufacturer. They sent one of their guys who said he had just left a pool with the same problem...calcium scaling. After speaking to his boss on the phone, he performed an acid wash using a descaler and acid. Instructions were to leave the filter off for 24 hours, then run the filter for 24 hours. After this process, there was no improvement! The person in charge of service for the manufacturer said it would take time, and the process may have to be repeated along with scrubbing the pool and spa. (problem is in both) That was almost 2 months ago. Since the acid wash, our pool guy set a descaling plan for us.... keep the ph at 7.2 and chlorine at 2, add a descaler weekly and no shocking. He said that this would slowly remove the "scale".
Today another pool company came out to look at a different issue, and took a look at our "scale". He has been installing (gunite) pools for 25 years or so and has experience with scale which he said is rough and can flake off. He was baffled. Whatever it is we have is smooth to the touch, just as smooth as the pool surface itself. There is no way to scrape it off. When the spa was drained, the "white stains" became snow white (no longer hydrated) and had a slight chalky residue when rubbed hard. I am so confused! Is this scale or not? Where do we go from here? It is so frustrating. I just made another call to the manufacturer for further assistance. I did send pics of the lines, etc. and the "white" drained spa to them initially.