Which of the following is not likely to be a control location?

The heating hot water system is not typically considered a control location for Legionella management because its primary function is to heat water for various uses rather than to actively cool or treat water where Legionella growth is a concern. Control locations are points in a plumbing or water system where conditions are favorable for the growth of Legionella bacteria and where intervention measures can be implemented effectively.

In contrast, cold water supply systems, shower fixtures, and cooling towers are all environments that can support Legionella proliferation if they are not properly maintained. Cold water systems, especially if not adequately treated or if temperatures rise, can create a breeding ground for bacteria. Shower fixtures can aerosolize water, creating a risk of inhalation of Legionella-laden droplets. Cooling towers are known to concentrate Legionella and have been associated with outbreaks, making them critical control points where management strategies must be applied to prevent contamination. Thus, the heating hot water system's role does not align with those of the other options, which are active surveillance and management points in Legionella control efforts.