Tank cleaning and disinfection of water systems helps manage the risk of Legionella bacteria growth. Annual tank cleaning is not always required, and the frequency depends on factors like inspection results, contamination risks, and water system usage. Tank water for non-drinking purposes like flushing toilets may only need cleaning every 3-5 years depending on water turnover and silt buildup. Proper signage can help mitigate risks of people drinking from non-potable water sources.