LaMotte Pool Manager Water Quality Handbook - Manual (Page 42)

Stains
When stains appear on swimming pool surfaces
immediate action should be taken to avoid costly and
annoying repairs. Brushing can often remove fresh
stains. Neglected stains in plaster pools may ultimately
require draining the pool and applying an acid wash to
the surfaces. Like colored water, stains are the result of
metal ions in pool water and they indicate that either
the source water contains metals (such as copper, iron
and manganese) or that a corrosive pool water condition
is dissolving metal pool components.
After noticing a pool stain, determine what caused it by
testing the water for metals. If the test indicates a metal
problem, the pH should be adjusted to be within the
proper range of pH 7.2-7.6. If the problem persists, add a
sequestering agent to chemically bind the metals to
keep them from causing staining problems.
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