Government agencies and industry groups have agreed for decades that waterborne Legionella bacteria cause Legionnaires’ disease and minimizing this bacteria in building water systems is the best strategy to reduce risk.  


Position papers have warned building water systems should be managed to minimize Legionella and guidelines such as ASHRAE 12-2000 have outlined control measures.

But now government agencies and ASHRAE are on the brink of solidifying agreement — not only about the need to manage building water systems for Legionella control — but about the approach to it.


It started in 2007 with the World Health Organization declaring “developing a WSP [water safety plan] is the preferred approach to managing… Legionella.” In 2010, ASHRAE essentially gave a thumb’s up to the WHO approach by outlining in the first draft of 188P a water management plan with the basic components recommended by the WHO. 


In August 2014, the U.S. Veterans Health Administration finalized Directive 1061, requiring a water management plan with the same essential components for all VHA facilities where patients, residents or visitors stay overnight.


The EPA appears to be on board as well, having outlined the same water management plan components in its April 28 webinar “Understanding End Water Quality in Hospitals and other Large Buildings.”



ASHRAE took comments on the fifth draft of 188P for a 30-day period ending April 12, 2015. As with previous drafts of the pending standard now titled “Legionellosis: Risk Management for Building Water Systems,” the basic strategy outlined for reducing risk is to implement a plan for managing building water systems. 


Drafts 1-3 called it a HACCP (Hazard Analysis and Critical Control Point) plan. In Draft 4, the overall principles remained the same but HACCP language was replaced with generic terms. With a couple exceptions, the differences between drafts four and five are mostly semantical. For example, “devices” is changed to “building water systems” in several places.


The Legionella risk reduction strategy set forth in 188P is to implement a water management plan for building water systems including cooling towers, evaporative condensers, whirlpool spas, ornamental fountains, misters, atomizers, air washers, humidifiers and other devices that release water droplets. For potable plumbing systems, a management plan would be required only in buildings that have any of the following: multiple housing units with a centralized hot water system; more than 10 stories; housing for occupants over the age of 65; health care for patients staying longer than 24 hours; or an area housing or treating persons at especially high risk of contracting Legionnaires’ disease.


To be consistent with ASHRAE 188P and the WHO and VHA documents, water management plans must include the following components:


A list of the water management plan team members.

Teams typically consist of 10 or fewer individuals who oversee the program and make decisions about it. Many others are needed to implement it.


A brief description of the building water systems with flow diagrams.

Salient information should be included for all building water systems, not just the ones prone to Legionella growth and transmission. Simple line diagrams should show where water is received, processed and used. 


For most facilities, at least two diagrams should be included: one for domestic (potable) water systems and another for utility (nonpotable) systems. Flow diagrams should be simple. Plumbing engineers must resist the temptation to add valves, equipment, scaling and other unnecessary details that clutter the diagrams and ultimately hinder their real purpose.


• Analysis of the building water systems.

Commonly referred to as hazard analysis, this is a brief explanation as to why each water system does or does not present a significant potential for Legionella growth and transmission and for those that do, whether it is a location at which Legionella control measures can be applied.


• Control measures.

Only what is actually done to water systems will reduce Legionnaires’ disease, so control measures are the most important part of any Legionella water management plan. The team must come up with a specific list of control measures for each building water system. ASHRAE 188P gives a framework for the team to fill in, stating that procedures must be included, as applicable, for new construction, equipment siting, startup and shutdown, inspections, maintenance, cleaning, disinfection, monitoring (e.g., temperatures; disinfectant levels) and water treatment. 


The team also must write out steps for responding to Legionnaires’ disease should a case occur despite the prevention efforts. Each control measure must be monitored to determine whether it is performed to the standard — called a control limit — designated in the plan. If the control limit is not met, then corrective action must be implemented. The monitoring procedure, monitoring frequency, control limit and corrective action must be listed for each control measure.


• Documentation and communication procedures.

Draft 5 of 188P instructs the team to “establish documentation and communication procedures for all activities of the Program.”


• Verification procedures.

The team or a designated “verification person” must review documentation to ensure the plan is being implemented. 


• Validation.

The effectiveness of the plan in controlling Legionella must be validated, by the team’s own testing or certified by a third party. Testing water systems for Legionella provides the most direct feedback on Legionella control. Legionella testing is discussed as a validation option in 188P but is not required.


Plumbing engineers and contractors

The recent draft of ASHRAE 188P lists responsibilities for designers, contractors, as well as owners.


For new construction or renovations involving water systems deemed to require Legionella control measures, engineers must provide documentation, diagrams or instructions as needed for monitoring and control, code compliance, operation and maintenance, control system operation, calibration, installation and startup, commissioning (including procedures for flushing and disinfection), filling and draining, equipment sizes, piping layout, system materials, pipe sizes, design flow rates, design temperatures and the impact of heat loss or heat gain.


Designers also must note locations of equipment access (or note inadequate access), filling and draining, flushing, sampling, temperature monitoring, treatment, no-flow and low-flow areas, possible cross connections between potable and nonpotable systems, and outside air intakes.


Proper balancing of plumbing systems must be documented in a report to the owner. Responsibility for balancing will begin with engineers in specifying valves and pass to contractors to perform the work.


Disinfection of plumbing systems will need to be carried out no more than three weeks before any part of the building is occupied for its intended purpose.


What’s on deck?

If the 188P committee decides the comments received on Draft 5 are not substantive enough to warrant a sixth draft, then the standard could be finalized as early as this July.


If and when 188P becomes a standard, it could be adopted as law by government agencies (e.g., state health departments). It already has been proposed for adoption into the International Plumbing Code and the International Mechanical Code. It almost certainly will be a key document for determining the “standard of care” in litigation related to Legionnaires’ disease.  


A standard would nudge plumbing engineers to do what they should already be doing: designing plumbing systems and writing specifications to minimize Legionella. It also could provide opportunities for plumbing engineers to provide services such as surveying facilities to gather information for water management plans and designing plumbing disinfection systems.


The biggest winners would be the people who avoid Legionnaires’ disease. Legionella control measures work — scientific literature is replete with reports of successful Legionella control and subsequent reduction in Legionnaires’ disease. If building operators implement the practices outlined in 188P, fewer people will suffer and die from Legionella infections.



Author bio: Matt Freije has specialized in Legionella prevention since founding HC Info ( in 1995. He has written two books, developed water management plans, taught seminars in five countries, and written and narrated nine e-learning courses including the new course “How to Survey a Building for a Legionella Water Management Plan.” His first book, “Legionellae Control in Health Care Facilities: A Guide for Minimizing Risk,” has been distributed in more than 30 countries.