pool stain recurring

b1r2a3d4April 19, 2013

This stain (crud growth) is on a modified plaster (many brand names) and I've drained the pool several times in the last 7 years and sanded the spots with a diamond disk. They initially are bumpy and can be knocked off with a sharp chisel, but a drain and sanding leaves the area beautiful and spotless and smooth. After a season the dark bumps begin growing again in the very same exact spots. Could this be a defect in the plaster since new that precipitates a growth? Is it some sort of mysterious fungus or algae buried in the plaster? The rest of the pool is pristine. I have auto HCl and Cl feeders that keep everything balanced perfectly.

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I can't tell from the picture but are they brown or rust colored?

I get similar spots in my PebbleSheen. Pool builder says it's a mineral leeching out of some of the stones. It always happens in the exact same spots. I've got about 9 dime sized and smaller spots that will reoccur a couple times per season. Tried everything to remove them. The only thing that worked, like magic, was absorbic acid. In other words, I had my 14 year old swim around, underwater, with a mask on and rub the spots with a simple Vitamin C tablet. 1000 mg.

I saw one post on here, where the pool got brown stains in the same spots but they were long. Turns out the rebar was rusting through the pool finish. Yikes.

    Bookmark   April 20, 2013 at 7:49PM
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Thanks for the message, banana. I've have metal stains which come from fertilizer from the adjacent golf course. These clear up really well with a handful of ascorbic acid, no problem. But the cruddy spots I have are actually nodules about 1mm above the surface. They don't have any distinct color, just dark. Like I said I can sand them off and they're gone and the surface looks perfect. I just don't get the position memory - every season, the same spots.

    Bookmark   April 20, 2013 at 10:17PM
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Here is a good place to start for stains see links below. You may want to try a test kit.

Hope this helps

Here is a link that might be useful: Jacks Magic

    Bookmark   April 21, 2013 at 11:13AM
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