How are these problems treated?
If metals are suspected to be present in source water, it must be tested before making any other adjustments to water chemistry. The metal content might need to be reduced first in order to avoid stains, scale and cloudy water. It is important to do this before adding any oxidizer such as chlorine, since, as previously discussed, it can oxidize metals into a more problematic form.
If using a copper-based algaecide or a mineral purification system, water will need to be tested frequently. Copper levels should be kept below 0.2 ppm or more serious problems than algae may occur.
Dip-and-read test strips can provide a quick analysis of the metals in solution, indicating iron and copper levels accurately in seconds. Liquid drop kits or test tablets are also available to detect low, but potentially harmful levels of iron and copper. All of these methods can also provide reliable analysis in a short enough period of time to be used at poolside.
With occasional testing in problem waters, keeping metal levels under control should be relatively simple. If detected, the typical way to eliminate or reduce the metal content in your water is with a sequestering or chelating agent. A sequestering agent is a chemical compound that can bind the metals into large particles. Once it does its work, the filter can intercept the large particles containing the metals, allowing them to be backwashed out. A chelating agent will work to suspend the metals back into solution. This method may not be a permanent fix and several doses of the agent may be needed. If metals are a recurring problem, weekly dosage with metal remover may be the best defence against potential metal-related problems.
Any metal treatment chemicals will work more efficiently if the pool water is properly balanced for pH, alkalinity and hardness. Therefore, these levels may need to be adjusted before adding metal-removing chemicals. Otherwise, the chelating agent will have to work harder to do its job, meaning operators will have to add more of it and spend more money. Again, be sure not to add any oxidizers, such as chlorine, until the metals have been treated. Always follow the manufacturer’s directions with this or any other pool and spa chemical for best results.
Testing and prevention
Metals may be a menace, but they can be easily controlled once you have identified the problem and the source. Regular testing and maintenance will prevent significant issues and costly and time-consuming clean up or repairs to rusty equipment. Inexpensive test strips or other testing methods can serve as insurance to prevent metal buildup and avoid much more expensive repairs.
Joe Sweazy is technical sales and services manager for HACH Company/ETS Business Unit, manufacturer of AquaChek®, TruTest® Digital Test Strip Reader, FastChek™ Pro Prescription Testing System and other water quality products. He has published dozens of articles on pool and spa water chemistry and has presented numerous seminars at conferences of the Association of Pool & Spa Professionals (APSP), Northeast Spa & Pool Association (NESPA) and the World Aquatic Health™ Conference (WAHC). He may be reached at jsweazy@hach.com.
