I just had my pool resurfaced in 2015 and in the last year it's developed a couple of stains that I'd like to see if I can get any pointers on how to remove. One type of stain is from pucks that were placed directly in the pool until they dissolved. The other seems to be... dirt? They're darkened areas primarily in the deep end where palm nuts drop, debris tends to collect, and the pool cleaner spends most of its time. However, these areas are completely unaffected by vigorous brushing, the cleaner, etc. so I'm not certain they're dirt. Nothing looks too bad, but the pool's surface is only a year old, and I don't like to think what it would be like if this pace keeps up for another 10 years. Any suggestions?
Stains On Gunite Pool
- Thread starter wsamon
- Start date
Re: Stains on Gunite Pool
This is the puck stain
![IMG_20160527_184512354[1].jpg](https://www.troublefreepool.com/data/attachments/41/41176-540f9ad25936535f1283392e9cc1a7c6.jpg "IMG_20160527_184512354[1].jpg")
and here is the "dirty stained" bottom of the pool
![IMG_20160527_184445324[1].jpg](https://www.troublefreepool.com/data/attachments/41/41177-a91e340c974f2db3cc2b50a50b4450b1.jpg "IMG_20160527_184445324[1].jpg")
This is the puck stain
and here is the "dirty stained" bottom of the pool
The puck stain is there for keeps. Trichlor is very acidic and it etched the concrete. I don't know if you've ever seen a concrete floor where someone has set a leaking car battery or if you've ever set a jug of pool acid down somewhere and left a ring, but it's the same.
The dark stains could be organic from tannins leaching out or metals or even something embedded in calcium scale. Can you dive down and feel it? Is it rough, or just dark? Rough and raised means Calcium scale. If smooth, set some cheap Vitamin C tablets on the stain for a few minutes and see if they left a white spot where they were. I mashed a bunch up and them them in a knee-high nylon with some smooth river rocks and pushed it in place with the pool brush. If there are clean spots, it's metals. Last test is -- believe it or not -- set a trichlor puck on for about five minutes. You've seen what happens when it goes too long. If it fades some, the stains are organic and elevated FC levels and time will fade them. Do the Vitamin C and the trichlor in that order, because the trichlor will also lift metals and may give you a false positive for organics.
The dark stains could be organic from tannins leaching out or metals or even something embedded in calcium scale. Can you dive down and feel it? Is it rough, or just dark? Rough and raised means Calcium scale. If smooth, set some cheap Vitamin C tablets on the stain for a few minutes and see if they left a white spot where they were. I mashed a bunch up and them them in a knee-high nylon with some smooth river rocks and pushed it in place with the pool brush. If there are clean spots, it's metals. Last test is -- believe it or not -- set a trichlor puck on for about five minutes. You've seen what happens when it goes too long. If it fades some, the stains are organic and elevated FC levels and time will fade them. Do the Vitamin C and the trichlor in that order, because the trichlor will also lift metals and may give you a false positive for organics.
Thanks for the tips! I'll try them out soon. The floor is as smooth as the rest of the pool, you can't feel the dark spots. If it is metals, what do I do? More vitamin C? For how long? If it's organic (wouldn't surprise me), how high does the FC need to be to clean it? I don't want to make the pool unusable for weeks dealing with this.
Bummer about the pool tab stain
I wish I had known that would be such an issue.
I think Richard320 is spot on. Hard to be exact but I bet they turn out to be organic stains. I would elevate the chlorine to twice the suggested level (depends on your CYA) and simply keep it there. Brush the stains when you can but they will probably lighten/disappear very slowly over maybe a couple of weeks. You can swim ANY TIME in that condition so you will lose no use of the pool.