What causes Iron stains in swimming pools?
You didn’t invite rust into your pool, so how did it get there? Iron stains typically occur when dissolved iron in your water reacts with chlorine or sunlight—a chemical process known as oxidation.
The iron usually enters your pool through two main sources:
- Source Water: Using well water is the most common culprit, as it is often rich in heavy metals, such as iron.
- Fertilizer: Fertilizers often contain high levels of iron to support plant nutrition. If fertilizer is blown or washed into the pool, it can lead to stains.
When this dissolved iron meets an oxidizer (like your pool shock), it precipitates out of the water and settles on your surfaces as reddish-brown ferric oxide—better known as rust. It looks permanent, but don’t worry; with the right science, it’s entirely reversible.
The Science of Removal: How It Works
Removing an iron stain is a lesson in chemistry. Since the stain was formed by oxidation (adding oxygen to solidifies the metal), removing it requires the opposite process: reduction.
Products like Iron Stain Treat™ use reducing agents to strip oxygen from iron oxide. This chemical reaction converts the solid, visible rust back into a dissolved, invisible form that can be suspended in the water.
Once the iron is lifted from the surface and dissolved, it is crucial to use a sequestering agent. This “locks up” the metal, preventing it from re-oxidizing and staining the surface again. It is a simple, direct, and guaranteed way to restore your pool’s sparkle.
