Diagnose copper vs. iron staining and apply sequestrant treatment

Steps

1. Identify likely stain type by color pattern: blue-green/teal often indicates copper, rust/reddish-brown often indicates iron, and dark purple/black can indicate manganese.
2. Confirm with a simple acid or ascorbic-acid (vitamin C) spot test: a stain that visibly lightens where the reagent touches it is metal-based; one that does not lighten is more likely organic staining or scale, not metal.
3. Test source/fill water for metals if staining recurs after refills, since well water or certain municipal supplies can be a recurring metal source.
4. For active stains, apply an ascorbic-acid-based or metal-specific stain remover per label directions before adding a sequestrant (chelating agent) to keep the freed metal suspended and prevent redeposit.
5. Once the stain is addressed, dose sequestrant according to measured metal ppm and re-dose periodically, since sequestrants break down over time and with chlorine exposure.