Building a Legionella water management plan that holds up

A water management plan (WMP) needs testing to prove it works. Testing is the measurable control step that shows the plan is doing its job and satisfies auditors.

Which rules apply

• ASHRAE 188: a WMP is required for buildings meeting population risk criteria. It sets no numeric limit. It is a process standard, so you write the control limits into your own WMP. It covers cooling towers, hot water systems, ornamental fountains and ice machines.
• CMS QSO-17-30: all Medicare and Medicaid healthcare facilities must have a WMP, and it must include routine Legionella environmental monitoring.
• NYC Local Law 77: all cooling towers must register, test and report to NYC DEP. Testing must be Legionella culture by an ELAP-certified laboratory. Legiolert does not substitute.

Where to sample

Any water system between 68 and 122°F can harbour Legionella. Focus on:

• cooling towers, the most common outbreak source
• hot water storage tanks, recirculating loops, dead legs and infrequently used outlets
• decorative fountains, whirlpool spas, hospital water systems and ice machines

Choosing the method for each round

Cooling tower response thresholds

Under 10 NYCRR Part 4, review and disinfect at or above 20 CFU/mL, and notify the health department above 1,000 CFU/mL.

What you get back

Reports give CFU/mL (culture) or MPN/100 mL (Legiolert), compared with the applicable thresholds or your WMP control limits, with corrective-action trigger language in a WMP record format. Sample on the schedule your WMP sets.