Water System Hazard Identification and Risk Assessment
Start with the system, not the hazard
Hazard identification begins with a complete water system description: every incoming source (municipal main, well, reclaimed, rainwater), treatment, storage, distribution, and every device that aerosolizes water. Draw process flow diagrams for each system separately: domestic cold, domestic hot and hot return, cooling tower or evaporative condenser, spa, fountain, fire protection with stagnant risers, irrigation, and medical equipment. Then walk the building and correct the drawings.
The hazard analysis
Rank each condition on three axes: can the organism enter and amplify here (temperature, stagnation, biofilm, sediment, dead legs, low flow, corrosion); can it be aerosolized or aspirated (showerhead, aerator, mister, fountain, cooling tower drift, ice machine, respiratory equipment); and who is exposed (transplant, oncology, ICU, NICU, dialysis, and surgical patients versus staff and visitors). Document the rationale, because exam items ask why a condition was ranked high.
Sentinel and high-risk locations
Transplant and oncology unit showers, ICU and NICU outlets, dialysis water, decorative fountains in patient areas, ice machines, and any rarely used fixture.
Traps
Considering only cooling towers; assuming municipal disinfection protects the building; missing undocumented dead legs, capped risers, and abandoned wings; ignoring construction, water main breaks, seasonal occupancy, and low-flow periods; treating "no cases yet" as proof of low risk; and doing the analysis once and never revisiting it.
Rule of thumb
Any outlet that produces an aerosol, holds water above about 25 °C, or serves an immunocompromised patient stays high priority until documented evidence lowers it.