Leading plumbers fear many of Melbourne's new apartment buildings pose a legionella bacteria risk due to their energy-efficient "warm water" systems.
The plumbers' concerns come as documents show Victoria's building regulator took nine months to exercise its power to demand a solution for the legionella risk in the warm-water system of North Melbourne's George apartments.
The systems store water at lower temperatures than traditional units and have become popular in recent years as developers seek to achieve six-star energy efficiency ratings. They rely on solar-powered boosters to heat water on the way to residents' shower heads.
But the cooler temperature for storage of between 25 to 40 degrees can encourage the growth of legionella bacteria, while solar energy does not always achieve high enough temperatures to kill it off.