Pool stains can be the hardest things to deal with and they can be hard to treat and identify. It can be very discouraging to see your beautiful pool surface marred by a large rust stain. But don’t panic just yet, it might not be as bad as it looks. I will cover some remedies for both rust stains and organic stains that you will find in your pool as well as how to tell them apart.
Rust stains usually come from an object that is dropped in your pool. It can be a screw in a toy that junior left in the pool all week. Recently I found two nerf guns on the bottom of a pool and when I moved one of them, sure enough, there was a nice sized rust mark on the plaster. The screw in the gun was the source of the staining. It can be from toy cars with metal rods in the wheel or any other toy with metal parts. I highly suggest only allowing pool toys in your pool, toys made specifically to be in the water.
I’ve also seen batteries explode in the pool. I suppose it is from the water pressure, but when that
happens it leaves a very nasty stain on the pool bottom. You will have a dark center portion and then a rust stain explosion from the center point. I have even had kids playing with a 10 lbs. weight in a pool and leaving it in there all week. It left a huge stain in a circular pattern. Bobby Pins and Clothes Pins are also a big source of rust staining. I find a few every year in a pool or spa and they leave nice thin stain all over the bottom. Fertilizer pellets are another source and, on the bag, it states not to get them in your driveway because of the staining it can create. When they are carelessly dropped into your pool they sit on the pool bottom and leave BB type stains all over the pool floor.
To remove these stains, you can rub the spot with a vitamin C tablet or apply Ascorbic Acid in powder form to the affected area. The stain will usually simply lift off after a few minutes or with your scrubbing. In a fiberglass pool, Ascorbic Acid is very effective in removing stains that cover the entire surface. If you can reach the stain with a Vitamin C tablet you can usually rub it off without any issues. For the areas, you might not be able to reach you can put some crushed Vitamin C tablets in a thin sock and set it over the stain. Another good option is the Stain Eraser which is a tool that connects to a standard pool pole and can be used to rub off a stain.
Something that looks a lot like a rust stain or metal stain is an organic stain. This is caused by organic debris like a leaf and sometimes dirt that will temporally stain the pool surface. It is usually a dark brown or black stain on the pool surface. Once you remove the debris from the pool bottom you will see the staining. Usually, the pool will have very low or no chlorine present in the water. To remove organic staining, you can raise the chlorine level up to shock levels and circulate the pool water. A good way to test if the stain is organic is to rub a 3” chlorine tablet on top of it. If the stain lifts immediately it was an organic stain.
Since I am talking about the 3” chlorine tablets, make sure one of these never falls into the pool and remains on the surface. These tablets also contain acid in the form of Cyanuric Acid and they will stain your pool surface very quickly. You will see a burn mark in the plaster in the shape of the tablet and these stains are hard to remove. So be very careful when you put the 3” Tablets into a floater and set it in your pool.
Metal staining can look like black or brown splotches on the pool surface. They are sometimes tough to identify and treat and in some cases, the only remedy is to drain and acid wash the pool. You can try some of the topical metal stain removing products like Bio-Dex Aquadex 50, Ascorbic Acid, Citric Acid, and the like. These products can be hit and miss especially if the metal stain is older. You can also help remove the stains with a metal sequestering agent likes Jack’s Magic Pink or Magenta Stuff. This will help suspend the metal ions in the water and then you can use a Culator 4.0 to extract the metal from the water.
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