Richmd Posted September 18, 2019 Report Share Posted September 18, 2019 I recently had the concrete around my pool sanded and painted. The workmen also sanded and spray painted the aluminum coping around the pool. After they vacuumed out the debris from the pool, the entire liner had a splotchy brown stain on it. The stain responded to Vitamin C and I successfully treated it with Ascorbic Acid. Is it possible that the aluminum dust from the coping caused this staining? I had just shocked the pool the day before they started work and the pH and alkalinity were good. Quote Link to comment Share on other sites More sharing options...
davidgreams Posted September 28, 2019 Report Share Posted September 28, 2019 It could be organic staining from the leaves, or it could be the beginning of black algae. Try sprinkling a small amount (one pound or so) of calcium hypochlorite so that the granules settle down onto the stain. Let the granules sit for a couple of minutes and then gently, VERY gently, use your nylon bristled wall brush to carefully "move them around" the stain area. If these are simply tannic acid stains from the leaves, the stains will come out (lighten, lessen, even go away) in a few minutes. We'll assume those are the beginnings of black algae colonies if the stains don't go away. If they don't, purchase a stainless steel pool brush (9-10" works fine) and a "3" tri-chlor puck holder" (both items mount on the pool pole you should have). Use the SS brush and vigorously brush the black spots - this breaks open the protective membrane that black algae builds around itself. Once you've brushed all the spots, mount a 3" tri-chlor puck in the puck holder and using the pool pole, rub the puck (a lot!) on the black spots. You'll want to do this about twice a day until the spots are gone. By using this method you won't affect the regular pool chemistry (much) and you'll concentrate your efforts on the fledgling colonies rather than the whole pool. Quote Link to comment Share on other sites More sharing options...
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