Stains – Discoloration or stains on pool surfaces can be a variety of colors and are often caused by metals present in the water.
Scale – Scale buildup is a rough white, gray or brown deposit on pool surfaces and metal objects caused when calcium in the water drops out of solution.
The Causes of Stain & Scale
Iron, copper and manganese are the most common metals occurring in pool water. When pH is low (below 7.2), these metals are “in solution” and will not stain pool surfaces. But when pH is raised, metals can drop “out of solution”, staining the pool surfaces and discoloring the water.
Chlorinating products and shock products can oxidize metals, making them more visible and resulting in unwanted staining. Copper can also be introduced to the water in copper-based algaecides.
Unwanted metal content in the water can come from the source water. It can also come from the corrosion of copper heat exchangers and copper piping caused by pool water imbalance.
There are three main conditions that cause calcium particles to deposit:
pH - High pH makes it difficult for calcium to stay suspended in the water. As a result, when pH rises, calcium can fall out of the water and deposit onto pool surfaces.
Water Temperature – Calcium becomes less soluble as water temperature increases, so as the water gets warmer the calcium can drop out of solution and deposit on pool surfaces.
Calcium Hardness Concentration – At some point, regardless of pH and water temperature, there can be too much calcium in the water to stay dissolved. As a result of this high calcium hardness levels, scaling can occur.
Stain and Scale Treatment
- Apply a scale, metal and stain control product directly into water.
- Brush areas where stains or scale are present.
- For metal staining, apply a filter aid to filter out some of the metals.
- Chemically clean filter after metals have been removed from pool.
- If the water has a high calcium level or if the fill water contains metals, apply monthly according to label directions to prevent stain or scale formation.