Preventing Legionella During Hospital Renovation and Water System Work

Renovation grows Legionella by disturbing the water system: shutdowns stagnate water, tie-ins open pipework, pressure events strip biofilm, and new dead legs give the bacteria warm, still water to colonize. Prevention is a water-management task run alongside the construction schedule — keep water moving or drain it, disinfect what was opened or stagnated, control temperatures, and verify before patients are exposed. Hospitals already carry this duty under their water management program; renovation is when the program earns its keep.

How renovation disturbs a hospital water system

Legionella lives in building water systems at low levels under normal operation. Construction changes the conditions in its favor:

• Stagnation: wings or floors taken out of service, capped lines, and little-used outlets leave water standing at growth temperatures for days or weeks.
• Dead legs: renovation creates them — abandoned branches, capped stubs “for future use,” and oversized runs serving fixtures not yet installed.
• Pressure events and intrusion: shutdowns, draining, and repressurization scour biofilm into the water column and can draw contaminants in at openings.
• Temperature drift: temporary systems and partially commissioned loops run in the Legionella growth range instead of at the facility’s control temperatures.

The prevention sequence, tied to the construction schedule

1. Before work: the water management team reviews the construction plan for every water-system touch — shutdowns, tie-ins, new branches, areas going out of service — and writes the flushing, disinfection, and sampling steps into the project plan, not as an afterthought.
2. During work: keep out-of-service areas flushed on a documented rhythm or drained and isolated; remove dead legs at the main rather than capping at the branch; maintain hot- and cold-water control temperatures in the occupied systems around the work.
3. At tie-in and commissioning: disinfect new and opened sections per the water management program (thermal or chemical, as the program specifies), flush to stable temperatures and disinfectant residuals, and complete any program-required sampling before the area returns to patient use.
4. On return to service: confirm results, document what was done against the plan, and put the new outlets and equipment on the program’s routine flushing and monitoring schedule.

Who owns what

The water management program — the ASHRAE 188-based structure most hospitals run, detailed in ASHRAE 188 Legionella water management plan requirements — owns the risk assessment and the control limits. The construction team owns executing the flushing, disinfection, and documentation steps in the plan. Infection prevention owns the patient-risk call: which units (transplant, oncology, ICU) get point-of-use filters or additional sampling while work proceeds. The broader construction water picture — beyond Legionella — is covered in water system risks during healthcare construction, and the general program framework in Legionella water management: ASHRAE 188, the CDC toolkit, and CMS requirements.

Why is Legionella a special risk during hospital renovation?

Renovation stagnates water, creates dead legs, opens pipework, and causes pressure events that strip biofilm — exactly the conditions Legionella colonizes. Immunocompromised patients exposed through showers, faucets, and medical water uses can develop Legionnaires’ disease, which is frequently fatal in this population.

When should a renovated water system be disinfected and sampled?

After sections are opened, stagnated, or newly installed — disinfection and flushing at tie-in and commissioning, with any program-required sampling completed and reviewed before the area returns to patient use.