If properly followed, American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) Standard 188 stands to affect the way water systems are managed in hundreds of thousands of buildings in the United States.

A number of existing government and industry guidelines outline procedures for minimizing Legionella in building water systems, so what makes ASHRAE 188, scheduled to be finalized later this year, such a big deal? First, it will be a Legionella standard, rather than just a guideline. It is slated to also become an American National Standards Institute (ANSI) standard, and may become law in some states. Laws carry more weight than standards, and standards more weight than guidelines. The second reason is that 188 is the first Legionella document in the United States to have such broad support among government agencies, industry groups, and Legionella experts.


The core requirement of the pending standard is the Hazard Analysis and Critical Control Point (HACCP) approach to the management of plumbing systems, cooling towers, decorative fountains, whirlpool spas, air washers, misters, and humidifiers.

The HACCP process wasn’t invented by ASHRAE. It has been used for years in the food industry and since 2007 has been advocated by the World Health Organization (WHO) in managing building water systems for the control of Legionella bacteria.

Legionella HACCP Water Plans

Developing a Legionella HACCP Water Plan for an office building, hotel, hospital, nursing home, or apartment building involves six tasks:

1. Form a team and appoint a leader.

Many people within and outside an organization will likely be required to carry out the procedures in a Legionella HACCP water plan, but the team that oversees the plan should consist of fewer than 10 people.

2. Perform a water systems inventory and construct flow diagrams.

This is not an inspection to identify or solve Legionella problems, or to assess the condition of water systems, and thus does not have to be performed by a Legionella expert. Any person familiar with water system components can do a survey for the purpose of developing a Legionella HACCP water plan because the objectives are simply to identify points and processing steps in the water systems. At a hospital, for example, the person best suited to conduct the survey might be the facility director or an engineer that knows where the water is fed into the campus, where it enters buildings, where it’s softened, heated, or otherwise processed, and the types of devices (e.g., faucets, showers, ice machines, dialysis connections) at points of use. Some owners will choose to hire an engineering firm or water treatment company to do the survey even though they could do it themselves.

3. Do hazard analysis summaries.

In HACCP hazard analysis summaries, the potential chemical, physical, or biological hazards are listed.

For a Legionella HACCP water plan, the only hazard to be specifically addressed is Legionella, so the hazard analysis is simply a matter of determining which water systems — among the ones identified in your survey — present a significant potential for Legionella growth and a significant potential for transmission from the water system to people.

4. Establish critical control points (CCPs).

Critical control points are points at which Legionella control measures can and should be applied.

5. Establish control measures, monitoring, frequency, performance standards (limits), and corrective actions at the CCPs.

This is the hard part.

Legionella control measures at the CCPs should be established for routine maintenance, design and construction, and responding to incidents like water main breaks and system shutdowns.

Control measures must be based on, and up to date with, scientific findings. They must also be reasonable in cost, practical, not overly complex, and clearly written so they are properly implemented.

Specific control limits must be established for each control measure, along with a monitoring method and frequency for checking to see if the control limits are within the target range. For example, if a control measure is to minimize buildup in cooling tower basins, then monitoring might be to inspect the basins weekly (the frequency), measuring the buildup of dirt and sediment, and noting the color of it. The limit could be one-half inch of buildup.

Corrective action would be specified to bring unacceptable control limits within range. For the cooling tower basin example, the corrective action could be to report the depth and color of buildup to the water treatment vendor, to clean the basin if the depth is greater than one-half inch or if the deposits are green, and to consider side stream filtration with sweeper jets — or more frequent cleaning — if buildup is repeatedly found at greater than one-half inch.

6. Establish documentation, verification, and validation procedures.

All measures must be documented. The designated “verification person” must check the documentation periodically to verify that the measures in the plan are being implemented.

The overall effectiveness of the plan in preventing Legionnaires’ disease must be validated.

After the HACCP Plan Is Written

Do what’s in the plan. If someone gets Legionnaires’ disease and sues the owner of the building suspected of being the source of Legionella that caused the illness, the plaintiff will likely examine the owner’s documents to determine if it had a Legionella HACCP water plan, if the plan was adequate, and if the plan was implemented. For legal risk, having a HACCP plan but not implementing it is almost as bad as not having one at all.

Train employees and key contractors so that they understand the plan’s procedures that apply to their jobs, and know how to do them.

Hold HACCP team meetings periodically to review verification and validation. Update the plan as needed based on validation results and new findings.

Is It Worth the Cost?

One could argue that ASHRAE 188 will overly burden facility budgets that are already stretched. However, most Legionella control measures are simply good maintenance so the ASHRAE standard should not significantly increase costs in buildings that are already well maintained.

Steve Sederstrom wishes Standard 188 had been released years ago. A project service manager for Johnson Controls in Harrisburg, Pa., Steve contracted Legionnaires’ disease in 2009 despite being a nonsmoker and only 47 years of age.

“My experience with Legionnaires’ disease in the hospital and recovery at home was the worst thing I have ever been through,” he said. “I missed more than two months of work and for five months had major memory problems — sometimes even forgetting where I was going. The one problem I still have is my memory — I’m afraid I will never get my memory back.”

Publication date: 7/9/2012