Re: Brown/yellow spots accumulating on plaster
Hi, welcome to the forum! I don't know what the brown powder is for sure, but I do know that I have used Ascorbic Acid (vitamin C) and it is very soluable in water. I would recommend you use a Mr. Clean magic eraser on the rust stains from the nails, or a very fine sandpaper. Rust stains don't seem to go away with vitamin C. My suggestion would be to take your chlorine up to shock level, or at least to the high point of your cya chlorine demand, which at cya of 30, would be 6ppms. The high chlorine level should break down whatever the powder is. Here is a chart that shows what the best levels of chlorine are to the amount of cya you have in the water.
Use the info in this chart to help you figure out what levels of chlorine you need to maintain in your pool based on the amount of CYA (cyanuric acid, also called stabilizer) that you have in your pool. (FC = free chlorine)
Stabilizer . . . . . . Min. FC . . . . Max FC . . . 'Shock' FC
=> 0 ppm . . . . . . . 1 ppm . . . . . 3 ppm . . . . 10 ppm
=> 10 - 20 ppm . . . . 2 ppm . . . . . 5 ppm . . . . 12 ppm
=> 30 - 50 ppm . . . . 3 ppm . . . . . 6 ppm . . . . 15 ppm
=> 60 - 90 ppm . . . . 5 ppm . . . . . 10 ppm . . .. 20 ppm
=> 100 - 200 ppm . . . 8 ppm . . . . . 15 ppm . . .. 25 ppm
As you can see you would need to take your chlorine up to 15ppms to reach shock for your water. The high chlorine levels will also help to lighten the rust stain. Feel free to ask any other questions you may have.
Northeast PA
16'x32' kidney 16K gal IG fiberglass pool; Bleach; Hayward 200lb sand filter; Hayward pump; 24hrs; Pf200; well; summer: none; winter: mesh; ; PF:7.5
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