Metal Sequestrant
A metal sequestrant is a pool chemical that binds dissolved metals (iron, copper, manganese) to prevent them from staining pool surfaces.
In Plain Language
When dissolved metals are present in pool water (from source water, algaecide, or corroded equipment), shocking the pool can cause them to oxidise and precipitate as stains. Metal sequestrant products (phosphonate or EDTA-based) bind metal ions in solution, keeping them from depositing as stains. They must be added before shocking when metals are suspected. They do not remove metals — they keep them in solution until they can be reduced through dilution.
Why It Matters
Adding shock to a pool with dissolved copper or iron without first adding a sequestrant is a common cause of blue-green or brown staining.
Typical Values
Last reviewed: 2026-06-01