Gunite pool with brown stains
First off, I am not very pool savvy. My pool is 30 years old. Last summer just before I closed I had some patches re-plastered and the pool acid washed. When I closed the pool it was very clean. I opened it and now I have some strange brown stains all over the pool. The water is crystal clear. The stains are not from leaves or metals(I have tested for that). I tried the Iron out test and the Chlorine tab test and neither changed the stain. I have tried brushing but nothing comes up. I also put granular on and nothing. My pool is very porous but it does feel smooth. I am at a loss! Any help would be greatly appreciated!
Re: Gunite pool with brown stains
I'm not sure what I'm seeing, beyond a not so good plaster job. There's a lot of reflection and also some image curvature due to surface ripples.
+ How exaggerated is the coloration in the 'enhanced' photos?
+ Is the plaster really as rough and uneven as it appears in the #2 enhanced detail and in the #3 enhanced views?
+ How did you test for metal stains?
+ Have you tried dropping a bag of calcium hypochlorite on one of the stained areas? If it's any sort of organic stain, that will tend to lighten it.
+ It *looks* like dirt stains in somewhat sloppy plaster repair, to me. Is that possible? Mineral based stains (like embedded clay or chert soil) is not removable.
Re: Gunite pool with brown stains
It was hard to photograph. the color is more of a light brown color and definitely less clay like in real life.
Some of the areas are porous but some of the places are slippery smooth. The patches were very smooth and even they are holding the "stain in some spots"
It was pure white at the end of last summer.
I tried vitamin C tablets both rubbing and leaving on.(no change)
I tried Iron out on a patch.(no change)
I took the water to Leslie's and they tested it and said no metal.
Last summer I had the patches redone because they were standing out from the summer before when they were patched. I also had him acid wash it to get the leaf stains out. They sanded and for the most part it really did look good. I had the same company plaster it a few years ago so he came back to "correct" it.
It does not seem to move with a metal brush. I think it looks like chemical to me? Is that possible?
I poured granular chlorine on the shallow end. (no change)
Re: Gunite pool with brown stains
+ Vitamin C + Iron Out, used separately, rule out any metals I've seen in a pool.
+ Cal hypo on a spot rules out organics, including algae.
? Is the brown ONLY on the patched areas or ALSO on other areas of the plaster?
Re: Gunite pool with brown stains
OK. Different info: "stains are everywhere" and not just the patches. Plus I could see a little better in one of your pictures (cropped, rotated, and enhanced below).
It looks to me like what's sometimes called "plaster mottling". Whether it's a defect or an inherent characteristic of modern pool plaster (which is missing some ingredients used 40 years ago, such as asbestos) depends on who you talk to -- but I can tell you it's quite common. (There's another sort of "mottling" that is more spots than streaks, that has other causes, and is a defect. But in that case, the argument is, is it a defect in the plaster or a result of water chemistry.)
Anyhow, the only fix for the first type of mottling is a replaster job - but it may reappear. Acid washing may reduce it, but at the cost of a rougher and more porous surface.
I could be wrong, however, so DO try the cal hypo.
https://lh4.googleusercontent.com/--...nh%2520det.jpg
click for full size view
