Fill or ground water can cause copper, iron, and manganese can find their way into the pool. The copper and iron can also be from metals in accessories like the pump or heater that are corroding due to improper water chemistry.
If the pool’s pH, total alkalinity, or calcium hardness level is low, then the water tends to be corrosive and the “rusting” of metal parts in the pool is greatly increased. Another common source of copper is copper-based algaecides. The cheaper ones often supply copper ions rather than complexes and, if too much is used, will result in green pool water.
If the water changes color after chlorine (or any other oxidizer) is added, the swimming pool water probably contains a metal.
What Happens if I Have High Levels of Metals?
How do I know which metal is present in my water?
- Green pool water usually indicates the presence of copper (more likely) or iron (less likely).
- Brown pool water usually indicates the presence of iron or, occasionally, copper.
- Purple or black pool water usually indicates the presence of manganese.
To solve the problem of colored water as a result of metals, there are two general approaches:
Shock the pool to oxidize the metal, which then settles out of solution and looks like rust. The rust can easily be vacuumed out of the pool.
Add a sequestering or chelating (ˈkēˌlāt) agent, which forms complexes with the metal and prevents it from being oxidized by the chlorine.
Prevent Repeat Problems:
If the source of the copper or iron cannot be established or if it cannot be avoided, regular addition of a chelating agent or sequestering agent (metal out products) will ensure that any new metal arriving in the pool water will be held in an inactive complex.