How to Clean Stubborn Stains from a Pool

The hard part of keeping a pool clean can be diagnosing what causes the stain. Cleaning the pool, once you know the issue, is relatively easy. 

One type of pool stain comes from natural materials. Leaves, nearby berries and other flora can cause a pool or its walls to change color. That particularly happens when the debris settles on the surface or even sinks to the bottom. Metals are another big cause of pool stains. Substances such as copper and iron can get into the pool from well water or corroded pipes. 

So, how do you tell the difference? Color is a differentiating factor. Green and brown stains are often caused by leaves. Red and blue splotches are created by berries. Now here’s a trickier possibility. Blue/green/black stains can be caused by berries, but if there aren’t any nearby, a corroded pipe is likely the culprit. Green/brown/red stains are often caused by well water or possibly the metal from a nearby fence, particularly a rusted one. Brown/black/purple stains are typically caused by manganese found in well water or city water supplies.

If you think the stain is caused by organic matter such as leaves or berries, apply chlorine directly to the stain. On the other hand, chlorine has little impact on a metal stain. If you think the issue is caused by a metal, apply ascorbic acid or vitamin C directly to the stain. If the stain is lightened or removed by the acid, it’s likely a metal stain. 

Natural treatments can clean stubborn stains from a pool, most commonly vinegar. The natural acidic substance will break down dirt, debris, and algae. To use this method, mix one part vinegar with three parts water. Pour the vinegar solution directly on the stain and let it sit for about 30 minutes before rinsing it off with a pool brush. You may need to repeat this process a few times to remove the stain. 

Another natural treatment method is using baking soda. Baking soda is a naturally alkaline substance that can break down dirt, debris, and algae. To use this method, mix one part baking soda with three parts water. Pour the baking soda solution directly on the stain and let it sit for about 30 minutes before scrubbing it off with a pool brush. You may need to repeat this process a few times to fully remove the stain. 

To clean the pool of a stubborn organic stain, raise the level of chlorine in the pool with a pool shock product. Before you do that, though, you’ll need to test the alkalinity and pH of the water. The alkalinity should be between 100 and 150 PPM (parts per million) and the pH between 7.4 and 7.6. 

If you have a small stain, use a regular dose of pool shock. If you have multiple stains, you may need up to three batches of the shock. That means three pounds of shock per 10,000 gallons of water. You also need to shock it at dusk or nighttime so the sun doesn’t burn away the chemicals. After shocking the pool, use a pool brush to scrub away the stains. Then run the pump for eight or so hours to help clean away the stain. Then brush the pool again to make sure the stains have been reached with the cleaning chemicals. If the stains don’t disappear, you may need to shock the pool again. 

Algaecides may be needed to kill algae and other aquatic plants. They can be found at most pool supply stores. Be sure to follow the instructions on the algaecide bottle. Pour the algaecide directly on the stubborn algae stains and let it sit for about 30 minutes before rinsing it off with a pool brush. You may need to repeat this process a few times to remove the stain fully.

To clean metal stains, first test the water for metals. Then take your water sample to a local pool store where they can help recommend the best cleaner for the job. Buy a metal pool stain remover that cleans the type of metal that stained your pool. Since these type of pool stain removers will work differently, make sure to carefully follow the instructions. 

If you want to make sure that organic material doesn’t stain your pool, be sure that those leaves and berries don’t settle in the water. Skim the pool surface regularly. Under the water level, a vacuum — robotic or handheld — can help keep the bottom and sides clean. If you can easily move plants with fruits and berries away from the pool area. definitely do so. Be vigilant about checking for stains and remove them early in the process. 

To prevent metal stains, test your water for metals. If you have them, use a hose filer whenever you fill your pool. Using a metal sequestrant will keep the metal material from binding onto pool surfaces, allowing the pool filter to remove particles.Also check your pipes regularly for corrosion, particularly if they’re made of copper. Don’t for get to keep your pH level in the acceptable range. A low pH will create acidic water, corroding the pipes and staining your pool.