Legionella Risk? Not in Your Building: Essential Water Safety Steps
- IHEA Membership
- May 5
- 4 min read
Dr Surani McCaw, B.E. (Chemical), Ph. D.
Ensure the safety of your building waster systems by following this comprehensive checklist to ensure Legionella-free water.
Checklist
1. Understand Incoming Water Quality
Chemical: Monitor conductivity, hardness, natural organic matter (NOM), residual disinfectant, chloride, sulfate, etc.
Physical: Regularly check temperature, turbidity, colour, and other physical characteristics.
Microbial: Assess heterotrophic plate count (HPC) to understand the biofilm formation potential.
2. Design & Implement Best Practices
Filtration Systems: Implement effective filtration (e.g., screen filters, water softeners) to minimise scaling and sediment buildup.
Water Velocity: Maintain water velocity between 1–1.5 m/s in the ringmain to minimise biofilm formation.
Hydraulic Design: Design systems to prevent stagnation and promote consistent flow to avoid conditions favourable to microbial growth.
Pipe Material Selection: Choose materials compatible with incoming water quality to reduce biofilm formation. Avoid copper and brass in low pH, soft water (low hardness and alkalinity), and water with a high chloride-to-sulfate mass ratio (CSMR).
Thermodynamic Optimisation: Perform calculations to maintain no more than ±5°C temperature variation to optimise system performance and energy efficiency.
Thermostatic Mixing Valves (TMVs): Install TMVs as close to the point of use (POU) as possible to keep blended water above 50°C and minimise storage below this temperature.
Cold Water and Blended Water Design: Avoid separate cold taps when TMVs supply both cold and blended water.
Real-Time Monitoring: Install sensors for continuous pH, temperature, turbidity, and oxidant level monitoring.
Data-Driven Systems: Utilise systems to detect early microbial activity for proactive intervention.
3. Maintain Appropriate Temperature Ranges
Hot Water Return: Keep hot water return temperatures above 55°C and cold water below 20°C.
Pipe Insulation: Use insulation materials (< 0.04 W/m·K) to minimise heat loss and prevent condensation.
Heating Elements: Ensure heating elements maintain temperatures above 60°C.
Temperature Uniformity: Continuously monitor and regulate water temperatures to maintain a consistent variance of no more than ±5°C across the distribution system.
4. Implement Preventative Maintenance Best Practices
System Cleaning: Regularly clean the system to remove sediment buildup and ensure optimal flow and system performance.
Scaling Control: Address scaling caused by calcium and magnesium deposits to prevent conditions that promote biofilm formation.
Routine Disinfection: Conduct routine disinfection of filtration equipment and associated pipework to maintain microbial control and system hygiene.
Flushing: All hot water system branch line outlets (including TMVs) should be flushed as often as necessary to ensure that all of the hot water in the branch line is replaced at least once a week
Performance Verification: Perform routine qualification, calibration, and validation of all equipment, including online monitoring systems, to ensure operational accuracy and regulatory compliance.
5. Routine Grab Sampling for System Health Check
NOM: Monitor NOM level to reduce biofilm formation. Be aware that NOM can elevate Assimilable Organic Carbon (AOC) and foster microbial growth.
Disinfectant Residuals: Maintain disinfectant residuals (e.g., chlorine, chloramine) at optimal levels to effectively control biofilm growth, while ensuring they are low enough to prevent corrosion of pipework and materials.
Corrosion Monitoring: Test water regularly for chloride and sulfate concentrations to prevent corrosion of metal pipework and fittings/fixtures.
Legionella Sampling: Schedule routine sampling (as per local guidelines) for both planktonic and biofilm-associated Legionella to ensure microbial safety. Ensure all results are verified by a NATA-accredited laboratory
Important
Grab sampling provides only a snapshot of water quality at a specific time and cannot serve as a stand-alone measure. Ongoing inspections, cleaning, and maintenance are essential for maintaining water safety.
6. Stay Compliant & Educated
Standards and Guidelines: Regularly review and stay updated with evolving Legionella management standards.
Training: Provide ongoing education and training for facility management teams.
7. Mitigate Risks in Critical Environments
Healthcare Settings: Pay special attention to healthcare environments, including cooling tower, bathing suites, dialysis units and Central Sterile Services Departments (CSSD) etc.
Health Requirements: Ensure temperature and flow controls meet stringent local health standards.
8. Align with Regulatory Standards
Risk Assessments: Perform regular risk assessments and document all compliance efforts to ensure adherence to safety protocols.
Redundancy & Preventive Maintenance: Implement redundancy measures and preventive maintenance plans to avoid operational disruptions and ensure ongoing legal compliance. When redundancy is in place, prevent water stagnation through frequent flushing to minimise biofilm formation
Local and National Guidelines: Strictly adhere to local and national water safety regulations, ensuring the system remains compliant with all applicable standards.
By adhering to these steps, you can safeguard your building’s water system, effectively minimising the risk of Legionella contamination and ensuring a healthier environment.
Dr. Surani McCaw is a Chemical Engineer with over 25 years of experience, specializing in water treatment for the healthcare and pharmaceutical sectors. She holds a Bachelor of Engineering (Chemical) and a PhD in water treatment from the University of NSW. Since 2008, Dr. McCaw has contributed to implementing National Healthcare Standards for CSSD and Renal Dialysis, focusing on cost-effective, risk-managed water technologies suited to Australia’s unique environment.
Hear Dr McCaw speak further on this topic at the upcoming IHEA National Conference.
Her presentation is titled ‘Legionella and Beyond: The Complex Interplay Between Water Hygiene and Corrosion in Healthcare Building Systems’.
Dr McCaw will speak at 4:00 PM on Tuesday 27th, Day Two of the Conference in Sydney.
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