Closed-loop systems are often regarded as virtually maintenance-free. Because the same water continually recirculates through a sealed system, it's easy to assume that once the system has been filled and chemically treated, the water will continue protecting the system indefinitely. It's an understandable assumption. Unlike open systems such as cooling towers, closed-loop systems aren't continually exposed to the atmosphere or losing water through evaporation, so they generally experience fewer water quality issues and operate with greater…