Hot water is often the main concern. When water is kept too warm rather than hot, it creates the perfect conditions for harmful bacteria to grow. One of the most dangerous is Legionella, which can cause a serious lung infection called Legionnaires’ disease. The bacteria thrive in water between 20°C and 45°C (68°F to 113°F), so maintaining hot water above 60°C (140°F) inside tanks and pipes is essential. At the same time, water is cooled at taps and showers to a safe 49°C (120°F) so people do not get burned.

Cold water matters too. When cold water rises above 20°C (68°F), it becomes another place where Legionella can survive. Well-designed plumbing keeps cold water consistently cool from the source to the tap.

Water movement is crucial. Bacteria multiply in stagnant water, so unused taps or pipes create hidden risk zones. Flushing systems and regularly using all taps keeps water moving and reduces stagnation.

Biofilm and sediment build-up also play a role. Over time, pipes and tanks can develop a slimy layer that protects bacteria from normal water flow and small doses of disinfectants. Routine cleaning and occasional chemical treatment, like chlorine or copper-silver ionization, remove these layers and help control bacterial growth.

Pipe design affects risk. Dead legs—sections of pipes that rarely see water—allow bacteria to flourish. Minimizing these sections and insulating hot water pipes to maintain temperature stability reduces potential breeding grounds.

Legionella infection is preventable, but it requires understanding how water systems work and taking consistent action. By keeping water at the right temperatures, ensuring regular flow, cleaning systems, and monitoring for risks, homeowners can protect their families from invisible dangers in everyday water.

Source: Building Systems Operations and Preventive Maintenance Course - Govur University