Iron (Pool Water)
Iron in pool water is a dissolved metal that can cause reddish-brown staining when oxidised by chlorine or shock treatment.
Definition
Iron in pool water is a dissolved metal that can cause reddish-brown staining when oxidised by chlorine or shock treatment.
Typical Values: Acceptable: below 0.2 ppm; Staining risk increases above 0.3 ppm
In Plain Language
Iron enters pool water from well water sources, corroding iron equipment, or certain algaecide products. Dissolved (ferrous) iron is clear in water. When oxidised by chlorine (especially during shock treatment), it converts to ferric iron (rust), which precipitates as a red-brown stain. Adding a metal sequestrant before shocking prevents iron from depositing on pool surfaces.
Why It Matters
Iron staining is one of the most common causes of unexpected brown discolouration in pools, especially after shock treatment.
Typical Values
Acceptable: below 0.2 ppm; Staining risk increases above 0.3 ppm
Last reviewed: 2026-06-01