All building owners, management corporations and town councils must continue proper maintenance of all water storage tanks and water pumps during the circuit breaker period, national water agency PUB said in response to queries about the risk of Legionnaires' disease in Singapore.

Under the Public Utilities (Water Supply) Regulations, they must carry out key preventive measures to ensure that water conveyed through the internal systems is safe for consumption, said a spokesman for the agency.

These include reducing the amount of water stored in the tanks, draining and refilling tanks and pipes with fresh water, flushing taps periodically and turning on taps not used for more than a week for five to 10 minutes before use.

These actions must be done during the circuit breaker period, and before business activity resumes, said the spokesman.

"During the circuit breaker period, water consumption at many buildings and premises is expected to be lower than normal due to reduced activity. Maintaining regular turnover of water tanks and flushing of pipes will ensure healthy levels of residual chlorine in the water supply and prevent harmful bacteria growth."

Professor Ooi Eng Eong, deputy director of the emerging infectious diseases programme at Duke-NUS Medical School, said Legionnaire's disease is a bacterial infection transmitted via contaminated aerosol or mist, such as those emitted by air-conditioner cooling towers.

He added that the National Environment Agency has regulations on how cooling towers, water fountains and sprinklers must be maintained to prevent the disease here.