Brown Stains in Saltwater Pool

I'm starting to get some brown staining in two areas of my Pebbletec saltwater pool. The Pebbletec is 6 years old as is the water in the pool.
My water quality has been OK - pH -7.4; alkalinity - 70-80; Cyanuric acid - 60-70; salt - 3500; Ca Hardness - 540. My free Chlorine has been low at 0.6 for several weeks due to problems with my Intellichlor IC40 chlorine generator cell. This cell was replaced today. I can't see anything in the water chemistry other than the high Ca hardness that could be giving me staining but I wouldn't expect this to be brown stains. I'm super chlorinating the pool now to get the chlorine residual back under control but I wonder whether I need to replace all my water in order to get my hardness level down. Appreciate any thoughts on how to combat and reverse(?) the staining other than acid clean and replace water.

Three tests:

1. Put some cal hypo powder on a stained area. (Cal hypo is usually available as bagged shock. You can probably buy a single bag at a pool store.)

2. Put a few Vitamin C tablets (ascorbic acid) on a stained area.

3. Put a few tablespoons of Iron Out (sodium hydrosulfite + sodium metabisulfite) on a stained area.

See what the results are.

I decided to empty my pool since my Ca hardness levels were so high and the pool water hadn't been changed in 6 years. Once the pool was empty the brown stains lightened up and looked more like rust stains. I decided I would try hydro jetting them off first with high pressure water and if that didn't work then I was going to try bleach and finally muriatic acid. The good news is that I was able to remove the stains quite easily in 30 minutes with the high pressure water. So I was able to avoid the chemical route. I'm refilling the pool right now.

Glad you were able to solve the problem.

But I'm still really curious about the cause of your stains. However, iron will absolutely cause staining. I have seen reports that improperly prepared pool salt may contain significant amounts of iron, so maybe that was the source.

Good luck!