Legionella bacteria are widely distributed in water systems. They tend to grow in biofilms or slime and are not completely eradicated by chlorination used to purify domestic water systems. Low and even non-detectable levels of the the bacteria can colonize a water source and grow to high concentrations under the right conditions, including the following
- Water stagnation: Encourages biofilm growth and reduces temperature and levels of disinfectant. Common issues that contribute to water stagnation include renovations that lead to 'dead legs' and reduced building occupancy.
- Water temperature fluctuations (The optimal growth temperature for Legionella is 68-122degrees F)
- Water pH between 5.0 - 8.5
- The presence of scale and sediment in water the promotes bacterial growth
- Other micro-organisms which can supply Legionella with essential nutrients for growth including algae and other bacteria, commonly referred to as 'biofilm'