Legionella Control: Preventing Pneumonia in Plumbing

Legionella pneumophila is a bacterium that loves warm water (20°C - 50°C). When we inhale tiny water droplets (aerosols) containing this bug, it causes a potentially fatal pneumonia.

Common Sources: Cooling towers, hot tubs, showerheads, decorative fountains.

prevention Strategies

1. Temperature Control (The Golden Rule)

• Keep Hot Water HOT: > 60°C (Bacteria die).
• Keep Cold Water COLD: < 20°C (Bacteria sleep).
• The Danger Zone: 25°C - 45°C is the prime breeding ground.
• The Protocol: Store hot water at 60°C+. Deliver it to taps at 50°C (install thermostatic mixing valves (TMVs) right at the tap to prevent scalding if needed, but keep the loop hot).

2. The Enemy: Biofilm

Legionella doesn't just float in water; it hides inside Biofilm—a slimy layer of bacteria and organic gunk that coats the inside of old pipes.

• Why it matters: Chlorine often can't penetrate thick biofilm. The bacteria hide inside, safe from chemicals, and release into the water randomly.
• Solution: You need strong oxidizers (like Chlorine Dioxide) or physical cleaning to strip biofilm.

3. Avoid Stagnation ("Dead Legs")

A "Dead Leg" is a pipe that leads to nowhere (capped off during renovation) or a tap that is rarely opened (like a guest bathroom in a hotel that is empty for weeks).

• The Risk: Water sits still, loses its chlorine, warms up to room temperature, and becomes a petri dish.
• Action:
  • Identify and remove all capped pipes.
  • Implement a Flushing Log: Turn on every unused tap/shower for 5 minutes once a week.

4. Chemical Disinfection Options

For high-risk buildings (Hospitals, Hotels, Nursing Homes):

5. Cooling Tower Maintenance (The Aerosol Factory)

Cooling towers are the #1 source of major outbreaks because they spray warm water mist into the air.

• Biocide Dosing: Must alternate between two types of biocides (to prevent resistance).
• Drift Eliminators: Install high-efficiency baffles to trap water droplets before they leave the tower.
• Deep Clean: Drain and scrub the tower basin twice a year.

Facility Maintenance Checklist

If you manage a building, follow the ASHRAE 188 Standard:

• Daily: Check calorifier (water heater) temperature is > 60°C.
• Weekly: Flush all low-use outlets (showers/taps) for 3 minutes.
• Monthly: Measure temperature at the "Sentinel Points" (nearest and furthest taps from the heater).
• Quarterly: Descale showerheads and aerators (scale hides bacteria).
• Yearly: Inspect cold water tanks for sediment/sludge.