Below are a few of the most common materials that lead to surface stains on the pool walls and floor. Their exact effects are always influenced by the water’s overall pH, oxidation-reduction potential, calcium hardness, total alkalinity, and saturation index.

  1. Iron (Fe)
    • Origins: Fill water, degraded pipes or equipment, impurities in salt.
    • Evidence: Green water; cloudy yellow, red, or brown water or surface stains.
    • Treatment: Sequestering or chelating agent; gentle brushing, or chlorine/acid wash for more severe stains.
  2. Copper (Cu)
    • Origins: Fill water, degraded pipes or equipment, copper algaecides, impurities in salt.
    • Evidence: Green, blue-green, yellow, brown, gray, or black color in water or plaster.
    • Treatment: Sequestering or chelating agent; gentle brushing, or chlorine/acid wash for more severe stains.
  3. Manganese (Mn)
    • Origins: Fill water, impurities in salt.
    • Evidence: Gray, black, lavender, or purple color in water or plaster.
    • Treatment:
      1. Sequestering or chelating agent; gentle brushing, or chlorine/acid wash for more severe stains or gray deposits on plaster.
      2. Gentle brushing, or acid wash for tougher deposits; balance pH and calcium hardness.
  4. Fertilizer Stains
    • Origins: Fertilizer pellets that get into the water will drop to the floor of the pool. These pellets contain iron and other minerals, which then stain the pool.
    • Evidence: Brown spots.
    • Treatment: These stains will go away on their own if the pool water is balanced properly.
  5. Leaf Stains
    • Origins: Leaves that have fallen into the pool and are not promptly removed.
    • Evidence: Brown stains where leaves have accumulated.
    • Treatment: These stains will go away on their own with elevated free chlorine in the water.