Subscribe to our newsletters & stay updated
The American Society of Sanitary Engineering International (ASSE) will be developing a new professional Qualification Standard on the heels of several major Legionnaires’ disease outbreaks in the U.S. According to a recent report in the Los Angeles Times, there has been yet another large outbreak of Legionnaires’ disease this summer.
The American Society of Heating Refrigeration and Air Conditioning Engineers (ASHRAE) recently published their new Standard ASHRAE 188, “Legionellosis: Risk Management for Building Water Systems.” The standard identifies building types that are at risk and how to set up a Legionella building water management plan and a team to assess the potential hazards associated with Legionella bacteria in building water systems.
Recently, New York officials adopted part of the ASHRAE standard as a means of controlling Legionella in cooling towers. The New York officials cited the sections in the ASHRAE 188 standard dealing with cooling tower maintenance, but failed to adopt the parts of the legislation that require a water management plan and a building water management team for each building. Those are essential components in developing a building survey of the building water systems, assessing the risk associated with Legionella in building water systems, and developing control strategies for reducing the risk of Legionella bacteria growth and being dispersed in aerosols that can be breathed in. This is how Legionella is transmitted from a water system to a person’s lungs.
Legionnaires’ disease is not transmitted from person to person. Legionellosis can occur when a person breathes in contaminated water droplets that have the bacteria in the water droplet. The bacteria get into the lining of the lungs, which serves as a petri dish for the bacteria to grow and colonize. Within two to 14 days. a victim will present flu-like symptoms and pneumonia (fluid in the lungs).
The most recent outbreak, as of this writing, was at the San Quentin Prison near San Francisco, Calif. There were about 100 prisoners who became ill with Legionnaires’ disease symptoms, and no deaths reported.
After six days of testing, officials still did not know what caused the outbreak. Many inmates were sick, and the sprawling historic prison was in near-lockdown. Showers and drinking water were shut off since a prisoner was diagnosed with the severe illness on August 27. In addition, prison officials said they were consulting daily with the U.S. Centers for Disease Control and Prevention as well as the state health department. As of September 3, there were 96 prisoners who showed symptoms of infection and seven inmates that had been hospitalized. Corrections and prison health officials said only six tested positive for the bacterium that causes Legionnaires' disease.
According to the Los Angeles Times, X-rays showed about half of the prisoners who were sick had a form of pneumonia. The medical office that runs prison health care expected the caseload to grow because they were still within the 10-day incubation period for Legionnaires disease. After about 14 days from the treatment of the water systems, the new cases should stop if the water systems are flushed, disinfected, and maintained at safe levels for water treatment chemicals. Officials said because Legionnaires' is caused by a water-borne bacterium, the state could not resume full water service within the prison until the source of the infection was found.
At first, San Quentin shut off not only water for drinking, but also for cooking, showers and toilets. Eventually the toilets were operable again. The 3,700 inmates at San Quentin were put on a breakfast-lunch-dinner diet of peanut butter sandwiches. Water trucks on some prison yards allowed inmates to bathe. That was not the case for those on death row, where some 730 inmates did not shower for more than a week.
There was also a recent outbreak of Legionnaires’ disease at a Veterans Administration (VA) facility in Quincy Ill., where at least 10 people died. Nine of the deaths were residents at the VA facility and four others in the nearby area were diagnosed with the illness. One person from the Quincy area (outside of the VA facility) died.
The Illinois Department of Veterans Affairs said on September 9 that it planned to disinfect water systems at the veteran’s facility with chlorine after previously cleaning its hot water tanks and air conditioning system and shutting down decorative and drinking water fountains and other potential sources of aerosolized water. The VA facility consists of 48 separate buildings on more than 200 acres, with 400 residents spread across eight buildings. At the VA facility, an epidemiological team from the federal Centers for Disease Control and Prevention remained at the 129-year-old facility, as of September 10, to assist with an investigation which was being conducted by the Illinois Department of Public Health. The source of the outbreak remained undetermined at the time of this writing. A spokesperson for the Illinois Department of Veterans Affairs said the age and size of the sprawling state of Illinois Veterans complex, "posed a very complex set of challenges" to both determine the source of the infectious disease and to prevent its spread.
Legionnaires’ disease is caused by Legionella bacteria that grows in warm water and is transmitted to the lungs of its victims in tiny water droplets that are inhaled. Common sources for this are cooling towers, air cooled mechanical equipment, showers, hot tubs, pools and any other source of water mist or aerosols of the building water systems.
Legionnaires’ disease is generally more severe in people with weakened immune systems. This explains why the VA hospital Illinois had up to 10 people dead with 53 people sick, and the prison in California had over 100 prisoners sick with no deaths. Hospitals and nursing homes need to be more cautious and take more care to prevent the bacteria from colonizing in their systems
There was also an even larger outbreak of Legionnaires’ disease in the Bronx section of New York City where 12 people died and over 119 people became ill. Officials said the cases elsewhere were not connected to the larger outbreak.
All of these outbreaks occurred in the peak summer months when Legionella bacteria is most active in warm waters. It takes two to 14 days for Legionnaires’ disease to fully develop in someone who has been exposed to Legionella bacteria. It takes several days to grow Legionella culture in a lab to determine the serotype. Knowing this, there must be no new cases for about 14 days before an outbreak can be declared over. Based on the incubation period, there could still be additional victims in the Illinois and California cases.
For response to outbreaks, we can control the conditions that promote Legionella bacteria growth by adding disinfecting chemicals immediately to cooling towers, pools, spas and decorative fountains. We can add chemicals to hot and cold water systems or raise the temperature of the domestic hot water systems to pasteurize the piping. I have noted that in many emergency heat and flush efforts, the mechanical system never brought the entire domestic hot water supply and return temperature up to disinfecting or pasteurization temperatures.
Figure 1 shows how Legionella reacts at various temperatures in degrees Fahrenheit.
It is possible to have events beyond the property line of incident locations. Disturbances can dislodge biofilm in the water main and provided a slug of highly concentrated biofilm and scale which could include a high dose of Legionella bacteria. Several things need to be investigated with each outbreak. Were the water system temperatures in the VA facility in the ideal growth temperature range for Legionella bacteria? Were there lots of “dead legs” or uncirculated dead end branches in the building piping system that allowed water treatment chemicals to dissipate and bacteria to flourish?
I have seen several proposals distributed for Legionella remediation work at government facilities that have a definition of a dead leg as anything over 25 feet long. My own experience and research using glass piping with colored water in the pipes clearly shows any time you have a dead end branch off of a flowing water main, like a branch to a hose valve or a by-pass, the water typically only circulates about 4 to 5 pipe diameters into the branch. The vortex or eddy current circulation in the branch allows fresh chlorinated water to circulate into the branch a distance equal to about 4 to 5 pipe diameters, which would allow water treatment chemicals to prevent bacteria growth within this distance. Beyond that distance, there will be stagnant water!
When air is trapped in branch piping, pressure disturbances in branches allow the stagnant water to move in and out periodically. This douses the piping system with bacteria. In order to prevent this condition, there are a few options:
Route the main line to within 4 or 5 pipe diameters of the by-pass valve, fixture or equipment connection.
Use a parallel branch circuit with a flow splitter fitting to assure flow into a looped fixture branch (this keeps all fixture branches flushed as downstream fixtures are used). This assures water treatment chemical flow up close to the fixtures.
Flush the fixture branch at intervals as needed based on the dissipation rate of the water treatment chemicals supplied by the water utility. In Germany, they require flushing to be done every three days in commercial and public buildings. And, it must be documented. Options are available for motorized valves to allow for automatic flushing and electronic documentation of the flushing.
With hot water systems, maintain the entire domestic hot water system above the temperature that Legionella will grow and multiply. ASHRAE Guideline 12 recommends 124°F. This requires temperature limit stops to be adjusted on showers and local mixing valves complying with ASSE 1070 can be use on other fixtures to reduce temperatures as required at the point of use.
I often hear of officials responding to an outbreak and testing for legionella. Testing for Legionella will confirm or deny you have Legionella. But, it won’t fix a system that has been set up wrong, or is being operated outside of its design conditions. I remember one outbreak where the system was designed so poorly they could not maintain temperatures throughout the system that were above the ideal Legionella bacteria growth temperature range.
The person responding to a Legionella incident and performing the Legionella sampling or testing typically has a checklist that requires emergency procedures for flushing the system, raising the system temperature to a disinfecting/pasteurizing temperature, or hyper-chlorinating the building water systems. The responding persons must also understand how the systems in a building are designed to be operated or how they should be maintained to control the system temperatures and provide the intended operating results and prevent conditions where bacteria will grow.
Engineers can sometimes design a system where the operating temperatures are in the ideal growth range. In these cases, water treatment chemicals should be considered or regular flushing should be done to maintain levels near the municipal water treatment levels. We must prevent the growth of Legionella bacteria in the system by designing it and maintaining it properly the first time, rather than curing or treating the effects of the disease by waiting for another outbreak and flushing and disinfecting the system again and again
Legionella risk management professionals should be trained to understand the mechanical engineering intent and design operating conditions for the system they are inspecting. They should be able to understand if the current system operating conditions could be contributing to Legionella bacteria growth. One cannot simply turn up system temperatures without making other adjustments to shower limits stops and temperature limiting valves to prevent scalding.
I have met Legionella risk management professionals who did not know what the components are in the mechanical systems, or how they work. I have also heard some people recommend using the thermostat on the water heater to control system temperatures to a specific temperature because mixing valves are too complicated to understand and can fail. That is like saying, “don’t use tires on a car because you can get a flat.”
These systems must be maintained. The model codes do not allow the thermostat on a water heater to be the final temperature control for scald prevention because the thermostat on a water heater is not accurate enough to prevent temperature swings that can allow scalding.
Sampling for Legionella will only confirm or deny the presence of Legionella at the time of the sampling. Control of Legionella starts with the system design and maintaining the system design operating conditions. Legionella prevention should also be included with commissioning and construction that complies with the design intent. Testing and balancing of the system should be done to verify the system is performing to the design conditions. Maintenance personnel should also be trained so that the maintenance personnel understand the system design intent and how all the components operate and how they should be maintained in order to maintain the design conditions.
This brings me to why a professional qualifications standard is needed for people who are designing, installing, and maintaining building water systems to prevent Legionella bacteria growth. Also for people responding to Legionella outbreaks, performing Legionella risk management surveys, and for building water systems management team members responsible for implementing water management plans to prevent Legionella in building water systems.
Water management plans are required in the new ASHRAE Standard 188, “Legionellosis: Risk Management for Building Water Systems.” There needs to be comprehensive training and a professional qualifications training program for these people. Legionella is preventable with proper system design, installation and maintenance. Health officials are going to have a limited understanding of engineering of building water systems. The opposite is true of the design professionals. They typically will have a limited understanding of the biology and the chemistry of Legionella and how it reacts at different temperatures and environmental conditions.
ASSE is in the process of developing a professional qualifications standard for Legionella risk management professionals. The details are not worked out yet, but preliminary meetings have indicated they will be developing different modules for system designers, installers, maintenance personnel, water treatment professionals, water management team members, and maybe an overall Professional Qualifications Standard for Legionella Risk Management professionals that respond to Legionella outbreaks.
There are several factors that seem to be increasing the number of Legionella incidents:
1. Increased awareness as media reports outbreaks and what causes Legionnaires’ disease outbreaks.
2. Efforts to reduce hot water storage temperatures to save energy have been attributed to some outbreaks.
3. Efforts to reduce hot water storage temperatures in an effort to try and prevent scalding has led to outbreaks in many cases. (without the use of master mixing valves conforming to ASSE 1017 or point-of-use temperature limiting devices)
4. Some people think tanks cause Legionella bacteria growth. Bacteria does not care if it is in a pipe or a tank, if the conditions are ideal for growth, it will grow.
5. Disruption of the scale/biofilm in the water main. This can dislodge high levels of Legionella bacteria from the walls of the water mains dosing systems that have ideal conditions for growth.
6. Water conservation efforts or reductions in water use associated with low flow plumbing fixtures. When water flows are reduced, the water is held in the system longer allowing the chlorine or water treatment chemicals to dissipate. The chlorine helps prevent Legionella bacteria from growing. As less water flows to plumbing fixtures, it causes water to flow slower in the water mains which are greatly oversized to allow for use of fire hydrants during fire incidents.
The conditions that promote bacteria growth could be reduced quickly with someone who is knowledgeable about Legionella prevention and the design and maintenance of the systems. In many cases where there is a Legionella outbreak, there has been a lack of awareness or knowledge of the operating conditions in building water systems that promote bacteria growth. Many outbreaks occur when the water system temperatures are maintained in the ideal temperature range for the water borne bacteria to grow and flourish. In many cases it is a lack of proper maintenance that contributes to the outbreak. This, coupled with an increase in the bacteria in municipal supplies in summer months and with reduced water flow rates from water conservation efforts, allows the water treatment chemicals in the water mains to dissipate to levels that are ineffective at fighting legionella bacteria in water mains.
Mechanical engineers, plumbing engineers and plumbing design professionals are the first ones in line with the opportunity to prevent Legionella bacteria growth by designing domestic hot water systems to prevent the growth of the bacteria in building water systems. They can help by providing plumbing designs that are in line with ASHRAE Guideline 12 recommendations of storing hot water at 140°F or higher and maintaining the hot water temperature at least 124°F throughout the entire hot water supply and return system. That means hot water return (HWR) systems that are designed using the ASHRAE/ASPE design method employing a 20 degree temperature difference from the supply to the return connection on the water heater would have a design temperature leaving the water heater of 144°F. And then, a minimum HWR temperature of 124°F just before the HWR pipe returns to the water heater.
Designers can double the circulated flow rate, which may require a slight increase in HWR pipe sizes to reduce the HWR system temperature differential to 10°F. This will then allow a temperature of 134°F leaving the water heater and 124°F returning to the water heater. Again, temperature limiting devices must be set and/or installed at all fixtures as required. This also makes it very important to have temperature gauges at the water heater outlet and at the HWR location connecting to the cold water line serving the water heater to know what the system temperatures are doing. Another temperature gauge could be installed on the CW inlet the water heater.
I am working with ASSE to develop a Professional Qualifications Standard that will provide educational materials and testing requirements for certification of Legionella professionals for minimizing Legionella in building water system specialists. This program should be approved and development underway after the annual meeting of ASSE in Phoenix, Ariz., at the Pointe Hilton Tapatio Cliffs Resort on November 3 - 7.
Ron George, CPD, is president of Plumb-Tech Design & Consulting Services LLC. He can be reached at: office 734-322-0225; cell phone 755-1908; and website www.Plumb-TechLLC.com.
© 2023 All Rights Reserved