Brown Stain on Top Step and Gray-ish Stains Elsewhere

[dclynds]

I've lived in this house with this pool for 2.5 years, but the house is 30 years old, so I assume the pool is also. Not sure when it was last re-plastered, but it's been a long time for sure (I also doubt it's ever been re-tiled, but that's for another discussion). Anyway, there are some very noticeable stains that I am curious about. About 50% of the top step has a brown stain and there are some areas deeper in the pool that have some gray looking stains. I assume the top step stain has to do with sunlight and poor circulation of water at some point, but that's just my guess as a newb. Can anyone tell from the picture what caused these stains and if there's some method to try to remove them or lighten them? If there's no trick, it's all good. I will just live with until I can afford to replaster it.

 

[Richard320]

Is the top step also rough to the touch? Because it looks like Calcium scale (grow your own sandpaper) with algae or dirt embedded in it. You can try sanding on that. I had reasonable luck with drywall sanding screen. Be aware that the stuff does shed and you'll have a lot of silt to vacuum up. To prevent it from happening again, you just maintain the pH and brush the area frequently.

If it's not rough, then it may be metal stains or organic stains. First test is to set a Vitamin C tablet on the stain for a couple minutes. If it left a white spot where it was, it's metal. There's a pool school article on that. If the pill didn't work, try setting a trichlor puck on the stain for a couple minutes and see if it lightened. If it did, it's organic. Maintaining higher than minimum FC levels and frequent brushing will fade it in a few weeks. Don't leave the puck on there, because they're very acidic. And do the tests in that order, because a trichlor puck may also lift a metal stain and lead you to believe it's something it's not.

 

[dclynds]

Thanks for the insight, Richard. I'll let you know what I find out

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