Legionellae vs. scalding in hot water systems:
a balancing act

By Ron George,CPD,
President, Ron George Design & Consulting Svcs.

I recently attended an American Society of Sanitary Engineering (ASSE) dinner meeting for the Michigan chapter at which the guest speaker gave a talk on the topic of Safe Water. The speaker had, unfortunately, lost two family members who died as a result of being exposed to Legionellae bacteria. They were in two different hospitals at different times for what were supposed to be routine hospital visits. The deaths were separated by time and location but tied together by the fact that, in both cases, they died of exposure to hospital acquired Legionnaires disease.

I am very familiar with the subject because I have served on the ASSE Legionnaires Disease research committee, and I am a certified Legionnaires Disease prevention specialist. I have attended numerous Legionnaires Disease seminars, and I have read books, guidelines and standard publications that address Legionellae bacteria in domestic hot water systems. I have also served as an expert witness on Legionnaires Disease cases.

The speaker talked about what happens when the water that we depend on becomes contaminated with the dangerous Legionellae bacteria, which got its name from an outbreak at an American Legion convention at the Belleview Stratford hotel in Philadelphia in 1976. Hundreds of people were sickened with flu-like symptoms, and 34 people died as a result of the outbreak. At the time the cause was thought to be a strain of the flu virus. When the bacterium was isolated, it was named Legionellae Pneumophilia. Legionellae refers to the American Legion, a kind of army, pneumo” means “lungs” and phila means “loving” in Latin. So, the bacterium that causes the illness is “an army of lung loving bacteria,” also known as Legionnaires Disease, a severe form of pneumonia.

Almost 8,000 people die every year from exposure to Legionellae bacteria in our water, and very little is being been done proactively to prevent it. That is almost three times the number of deaths from the September 11, 2001, terrorist attacks at the World Trade Center in New York. The speaker pointed out that this would be like an event as tragic as September 11, 2001, happening once every four months in our country Legionnaires Disease typically makes national news when there is an outbreak that involves many people. People who are exposed experience varying degrees of the illness, based on the strength of their immune systems. Those with weakened or suppressed immune systems fall gravely ill, and many of them die.

Legionellae is ever-present in water, and it is found naturally in the environment at low levels. When water is introduced into our manmade plumbing systems, with their warm ambient conditions, those low levels of Legionellae grow rapidly to dangerous levels. Study after study since the 1980s has proven that the plumbing systems of 70% of our hospitals are contaminated with high levels of the bacteria. Since the bacteria is resistant to chlorine and since chlorine rapidly dissipates in hot water, which is where we need Legionellae protection the most, treated chlorinated water is usually not sufficient to kill the bacteria.
Legionellae outbreaks occur in hospitals because they have a large population of people with suppressed immune systems. Healthy people will typically not develop an infection, even when exposed to high bacteria levels; a healthy immune system usually fights off infection. A patient with a suppressed immune system who comes into contact with water droplets that have a high concentration of Legionellae bacteria can become infected. Water in the form of aerosolized droplets can also come from a cooling tower or from water mist sprayers used for cooling people in hot climates. The person typically cannot see the water vapor droplets and unknowingly breathes the contaminated droplets into their lungs. Once the contaminated water droplets get to the warm moist lining of the lungs, the bacteria grows and multiplies, causing Legionnaires Disease, which is often misdiagnosed by doctors as pneumonia. Without specific laboratory tests, the disease is indistinguishable from any other bacterial pneumonia.

The Centers for Disease Control and Prevention (CDC) now realizes that the 18,000 confirmed cases of Legionnaires Disease reported each year represent approximately three percent (3%) of the real number of cases. The number of cases misdiagnosed as pneumonia is closer to 600,000 per year. The other 97% are typically misdiagnosed as regular pneumonia and, without the proper antibiotic treatment, can be fatal. With the proper treatment given at the onset to high risk people, Legionnaires Disease is no more fatal than the common flu.

One would think that 35 years after Legionellae was discovered, 25 to 30 years after research found a way to control and prevent its growth, 20 to 25 years after several types of water treatment technology was developed specifically for Legionellae prevention and after the last 12 years of several industry-sponsored guidelines being published, we would see a sharp decline in Legionnaires Disease in recent years. Sadly, that isn’t the case. In fact, despite all we know about how to prevent Legionnaires Disease, we continue to see an increase in confirmed cases. The increase may be the result of heightened awareness and more pro-active Legionnaires Disease testing. It may also be attributable to lower flow shower heads that break up shower head discharge flows into a finer mist, making the water easier to inhale.

We know how to prevent Legionellae bacteria from growing in the plumbing systems, and we have simple cost effective strategies to use. People do not have to lose their lives. With a mortality rate of nearly 40%, Legionnaires Disease continues to be among the deadliest preventable diseases known to us.

Why do we see a preventable disease continuing to increase? There can be many reasons, including the fact that the CDC has taken the position that, if you look for Legionellae bacteria, you are going to find it and, unless you can prove that the bacteria is causing a particular illness, there is nothing that a hospital, nursing home or facility with an at-risk population is required to do.

The CDC’s position does not go as far as requiring testing. It states that, unless there are two confirmed cases within a six-month period, a hospital is not obligated to do anything to clean up its water. Testing patients for Legionellae could be discouraged, because they might find it and would then be obligated to spend money to do something about it. If the patient dies, it can be written off as common pneumonia.
The absence of safe water protocols by the CDC gives hospitals an excuse to do too little. Too many people are losing their lives unnecessarily. A book titled Legionellae Control in Health Care Facilities, a Guide for Minimizing Risk by Matthew R. Freije and James M. Barbaree, Ph.D. is an excellent reference book for any facility (healthcare or otherwise) that either is concerned about Legionellae in its water systems or that wants to establish a proactive program to reduce the risk of the bacteria in their water supply.

The engineering community and the plumbing community need to be more proactive in designing preventative measures into plumbing systems. Copper silver ionization units on the water supply to the hospital and ultra-violet radiation units on circulated hot water systems have proven to be effective at limiting Legionellae bacteria growth in the water supply. Hot water storage temperatures above 135 to 140 degrees Fahrenheit, which is hot enough to kill the bacteria, should also be utilized. Hot water systems should also be circulated to prevent stagnant areas where bacteria can grow. Temperature-actuated master mixing valves can be used where appropriate to limit the distribution temperatures to a safe temperature that will not increase scalding hazards, or point-of-use temperature limiting devices should be used to prevent scalding. A good design uses this method to balance the concerns of

Legionellae with the concerns for scalding and thermal shock.

The speaker mentioned that she had a conversation a few months back with the author of the Occupational Safety & Health Administration (OSHA) Technical Manual on Legionnaires Disease. OSHA regulates Legionellae in the water but does not require proactive prevention. The author of the manual said, “The absence of strong guidance from the CDC on this topic amazes me. They are lax. If the disease you are tracking is continuing to increase why bother tracking it if you aren’t going to do anything about it.”

Although we currently lack federal regulations, there are literally dozens of Legionellae prevention guidance documents available for designers and engineers from such organizations as the Department of Defense (DoD), the Veterans Administration (VA), the American Water Works Association (AWWA), Occupational Safety & Health Administration (OSHA) and the American Society of Heating Refrigeration and Air-conditioning Engineers (ASHRAE).

One organization is taking a big step forward for water safety. Last year, ASHRAE released a draft standard for preventing Legionellae associated with building water systems. This will be the first standard of its kind and, when it is published, it will arguably result in a shift of responsibility being placed on building owners, mechanical engineers and contractors to proactively address Legionellae prevention.
I would encourage you to learn everything you can about the latest research surrounding Legionellae prevention, and I would strongly encourage you to become familiar with the new ASHRAE standard 188. The ASHRAE standard uses simple strategies, but it is going to require more than just removing dead legs in the hot water piping system, elevating the temperature of hot water storage tanks and keeping water moving with recirculation systems. Studies have now shown that those common practices are not enough.

The ASHRAE standard takes into account that the difficulty with Legionellae is that it can survive in a wide range of temperatures, with its ideal growth range being between 95 F-118 F. This is precisely in the temperature range at which hot water is delivered in a hospital and in most other types of facilities. The ASHRAE standard is going to require not only that domestic hot water be circulated but also that this be done with a minimum return of 124 F in healthcare buildings, thus keeping the water out of the ideal growth range parameters.

This certainly may change the way that you have been designing your domestic hot water systems. The elevated supply temperature is needed to meet the ASHRAE standard and will also mean that there is a need to use localized mixing valves that conform to ASSE 1070 or ASSE 1016 to limit hot water temperatures to safe temperatures. When using localized mixing valves is not feasible, you will need to include in your design the use of a physical or chemical secondary water treatment system. You can include one or more of the six ASHRAE allowable systems which are as follows:

• Chlorine injection systems
• Chloramines
• Chlorine dioxide
• Ozone
• Copper-silver ionization units
• UV irradiation

These are the systems that ASHRAE recognizes as having sufficient research to prove their effectiveness at controlling Legionellae bacteria. Engineers and designers should take the time to learn more about these systems as each one comes with its advantages and disadvantages, and each one of your designs may benefit from one type over another.

Call your local hospitals and ask them what they are doing to protect their patients from contracting Legionnaires Disease. If they aren’t doing anything, ask why not. Call your local newspapers and ask them to do a story on the topic to help increase awareness and education for your community. Legionnaires Disease is preventable. Hospitals are being sued because of the infections they cause, even when their infection rates are within national norms but, for preventable infections, the only acceptable rate is zero. Complacency is simply no longer acceptable.

Plumbing engineers and designers play a greater role in Legionnaires Disease prevention than do doctors, infection control professionals, HVAC engineers, water treatment specialists and microbiologists. The ASSE mission statement, “Prevention rather than cure,” dates back to the founding fathers of the organization in 1904. In an effort to prevent the unnecessary loss of life, engineers, designers, inspectors and contractors should all strive to design and install plumbing systems to prevent Legionellae bacteria growth, rather than dealing with trying to cure people who have contracted the disease.

Ron George is president of Plumb-Tech Design & Consulting Services. He has served as Chairman of the International Residential Plumbing & Mechanical Code Committee. To contact Ron, write him at rgdc@rongeorgedesign.com.