Step 15 = Set your hot water to at least 46 degrees C.
If the hot water flowing from your taps is too cool, then bacteria can thrive in the pipes and spray out in the water stream, potentially making you very ill indeed. A particular worry is Legionella bacteria, which cause Legionnaires' disease - a form of pneumonia which can be fatal to those with delicate lungs (young children, the elderly, asthmatics etc).
Legionella bacteria are kept at bay by water temperatures of 46 degrees Celcius and above. Fear not about cold water pipes - Legionella are dormant below 20 degrees Celcius.
If you have young children in the house, or elderly family members then it is a good idea to set the hot water thermostat to 46 or 47 degrees Celcius, much hotter would risk burns by scalding water. To be sure of the accuracy of your thermostat, periodically test the water flowing from the hot tap with a thermometer.
If you have taps or shower heads which are left dormant for two weeks or more, then they could be a breeding ground for Legionella. It is when Legionella bacteria are dispersed in water droplets that they can be breathed into the human body, so a neglected shower head should be immersed in a bucket of disinfectant (such as Milton) before being turned on. A neglected tap / shower should then be left running at 60 degrees C (the temperature which kills Legionella bacteria) for at least 5 minutes.
So go and check your hot water thermostat...