Guide for Metals in Pool Water

What are metals in pool water?

Copper, iron, and manganese can find their way into the pool from the fill water or the ground. If a well is used, the source may contain these metals in their ionic states. The copper and iron may also be the result of corrosion of the pool's pump, heater, pipe work or other metal accessories.

Ion generators or ionizers use D.C. electricity to "erode" electrodes composed of copper, silver and sometimes zinc. The result is free ions of these metals in the swimming pool water. At low concentrations they are effective in combating a range of algae, bacteria and viruses in conjunction with a low oxidizer level (such as chlorine). At high concentrations, these ions are oxidized by the chlorine (or other sanitizer), resulting in clear but colored water.

Today, pool water has very little, if any, contact with metal parts unless essential (e.g. pumps are plastic, while heat exchangers have to be metal, usually stainless steel). If the pool's pH is low or the total alkalinity is low or the 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 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.