A tragic case of individual with an intellectual disability being scalded by hot bathwater has raised the issue here in Alberta of whether caregivers should lower hot water tank temperatures to prevent scalding. One’s immediate reaction might be to lower water temperatures to a safe level. Typically this is described as 120° F or 49° C. Doing this will greatly reduce the risk of scalding, save a few dollars on medical bills, and be good for the environment.
BUT WAIT! Lowering your water heater temperature to prevent scalding could actually increase the risk of life threatening pneumonia, and pose an unacceptable risk for individuals with MECP2 Duplication Syndrome or other conditions that weaken the immune system. Legionella bacteria can thrive in hot water heaters that are set not to exceed the 49° C (120° F) temperature limit recommendation. In fact, contaminated water heaters are implicated in a large percentage of the sporadic cases of legionnaire’s disease that are recorded each year. This is a serious variety of respiratory infection with fatality rates reported between 5 and 30%. This grim statistic is likely to be higher among individuals with compromised immune systems such as those with MECP2 Duplication.
You may be thinking that Legionnaires Disease is rare and therefore not too much to worry about. In fact this is not a rare disease, it is quite common. The Center for Disease Control reports 8,000 to 18,000 people hospitalized each year in the US, with a fatality rate of about 15%. However, they point out “many infections are not diagnosed or reported, so this number may be higher.” In many cases of pneumonia no specific bacterium is ever identified, so some experts suggest the real number could be well in excess of 100,000 cases per year resulting in at more than 10,000 deaths. It is now recognized as one of the three major causes of pneumonia. In 2003, writing the American Journal of Respiratory Medicine, Sabria and Campins indicated that only 2% to 10% of actual cases were diagnosed and reported.
A study undertaken in Quebec (Dufresne, 2012) found that at least 14% of cases of of sporadic community acquired legionnaire’s disease could be traced to colonies of in the hot water tanks in the patients homes. It also reported that water temperature in the tanks was an important variable. In 11 of 31 homes the hot water tank temperature was 57° C or higher, and no legionella was present. In the remaining 20 homes, water temperatures were 56° C or below and 8 (40%) were found to have legionella bacteria present. While the other residents of these homes did not develop pneumonia, the subjects of this study became ill because they had risk factors associated with weak immune systems. The patients in this study were seriously ill; 97% were hospitalized and 36% died. Other studies have found that healthy individuals with functional immune systems living in the same homes simply show elevated antibodies indicating that they have been exposed and developed resistance to the legionella, but individuals with AIDS, transplant or cancer patients, people of advanced age, diabetics, or those with other conditions that weaken the immune system become seriously ill if they inhale droplets of contaminated water , frequently in showers or while bathing.
S. F. Dufresne, M.C. locas, A. Duchesne, C. Restieri, J. Ismaiån l, B. Lefebvre, A C. Labbeål , R. Dion, M. Plante & M. Laverdière. Sporadic Legionnaires’ disease: the role of domestic electric hot-water tanks, Epidemiol. Infect. (2012), 140, 172–181.
In 2006, an outbreak of Legionnaires’ disease at North Central Baptist Hospital in San Antonio infected 10 people and 3 of them died. According to the subsequent lawsuit, “temperatures of the water within the [hot water] tank were not in the desired range of 140 degrees Farenheit.” The hospital settled the claim for $5.2 million.
While most of the research has focused on legionella bacteria, there is at least one other serious pathogen that multiplies in low-temperture water tanks. NTM Non, non-tuberculous mycobateria, also thrives and has been transmitted to humans in low-temperature hot water heaters, This may be of particular concern to families of individuals with MECP2 Duplication Syndrome, since it has a strong affinity for those with weak immune systems.
It is because of this risk that some safety authorities are backing away from these lower maximum temperatures and recommending tank temperatures of 55° or 60°. Of course, water this hot can cause serious scalds, and so other precautions must be in place to prevent scalding. For, example pressure mixing valves can ensure that temperatures at the tap are lowered to a safe level.
Here in Alberta, 2011 Alberta Health Legionella Prevention and Management Guidelines require us to ” Maintain water-heater temperature in facilities to a minimum of 51° C and ensure that all hotwater temperature remains above 50° C at all distribution points.” However, recent studies suggest that tank temperatures of 60° C provides much better protection, and in most settings a tank temperature of 51° cannot provide continuous water temperatures at the tap above 50°.
This is particularly important for people with weakened immune systems. While legionella pneumophila is the bacterium that causes the well-known legionnaire’s disease, there are 34 other varieties of legionella that can cause serious pneumonia in people with weakened immune systems.
Adding to the argument against turning down the water tank temperature to prevent scalding is the opinion of experts that lowering the tank temperature is an effective safeguard against scalding . They point out that the actual temperature in hot water heaters varies substantially and even when the water at the bottom of the tank, where it is typically measured may be 49° C and considered safe, the water coming out of the top of the tank may be as high as 59°, hot enough to cause immediate burns. This is part of the reason why thermostat controls on water heaters are not labeled in degrees. They are simply not engineered to provide to provide water at specific temperature. As a result, depending on the water heater thermostat to protect against scalding may actually increase risk since people may thing other precautions are not needed.
So how do we balance the risk of scalding with the risk of infection for people with weakened immune systems? There is no easy answer that fits every situation. The best solution in these cases seems to be keeping a higher temperature in the hot water tank and using other methods to control the risk of scalding at the tap. For individuals with immune compromise, I recommend consulting a knowledgeable physician or immunologist before making a decision to turn down the temperature of the hot water heater, particularly for electric powered heaters. which seem to pose s greater risk.
Here is what some others have to say about this:
Water sources that frequently provide optimal conditions for growth of the [Legionella] include:
- domestic hot-water systems with water heaters that operate below 60°C (140°F) and deliver water to taps below 50°C (122°F);
The number one cause of waterborne disease outbreaks in the United States is not contaminants leaving the water treatment plant (we do a good job of killing those). It’s the pathogens that grow in home water heaters.
This same article (by Janet Raloff) goes on to say:
Infections due to these home-grown germs are estimated to kill 3,000 to 12,000 Americans annually, Edwards says…
140 ºF will kill a number of potentially lethal waterborne organisms, like the ones responsible for Legionnaire’s disease and NTM, short for nontuberculous mycobacterial infections. In contrast, 120º provides a nurturing environment for such toxic microbes.
We probably are all susceptible to infections if concentrations of the microbes get high enough. But studies in the United States and Europe have identified certain populations that appear especially vulnerable. These include people with HIV, individuals with cystic fibrosis, and especially slender senior citizens.
Water heater thermostats do not control temperature. I cringe every time I hear a radio talk show host or some one tell people to turn their water heater thermostats down to prevent scalding. Turning the thermostat down will not prevent scalding. I see the same misguided advice dispensed in newspaper handyman columns that talk about water heaters or home safety. Water heater thermostats cannot be relied upon to control the hot water temperature to a hot water system. Although water heater manufacturers recommend that installers set thermostats at 120 – 125 F, and although most of them ship the water heaters at lower temperature settings, it is impossible to accurately control the water heater temperature with a water heater thermostat. The plumbing engineering community continues to recommend storing hot water at 140 degrees Fahrenheit and mixing the hot water with an ASSE 1017 thermostatic valve to deliver hot water to the plumbing system at about 120 degrees Fahrenheit. This reduces the threat of Legionella bacteria growth in the tank, and allows a smaller water heater than one with a lower stored temperature.
Clinical Microbiology Reviews: “Legionella and Legionnaires’ Disease: 25 Years of Investigation “
Barry S. Fields, Robert F. Benson, Richard E. Besser (2002)
In 2000, ASHRAE [the American Society of Heating, Refrigerating and Air Conditioning Engineers] issued guidelines for maintaining water systems to minimize the likelihood of Legionnaires’ disease transmission. These guidelines recommend maintaining water systems at temperatures unfavorable for the amplification of legionellae. However, many states have regulations that limit the water temperature in health care facilities as a means of reducing scalding injuries. In Great Britain, elevated water temperatures were recommended as the primary means of preventing legionellosis in hospitals in 1991. Thermostatic mixing valves are used to reduce the likelihood of scalding. Adoption of these guidelines has resulted in a dramatic decline in nosocomial Legionnaires’ disease without increased reports of scalding. [emphasis added]
United Kingdom Health and Safety Executive, Control of Legionella Bacteria in Water Systems
The organisms do not appear to multiply below 20°C and will not survive above 60°C.
water in the calorifier should be brought up to 60°C for 1 hour before being used
It is recommended that hot water should be stored at 60°C and distributed so that it reaches a temperature of 50°C within one minute at outlets. Care is needed to avoid much higher temperatures because of the risk of scalding. At 50°C the risk of scalding is small for most people but the risk increases rapidly with higher temperatures and for longer exposure times. However the risk, particularly to young children, or the handicapped or elderly, and to those with sensory loss will be greater.12,13 & 14 Where a significant scalding risk has been identified, the use of TMVs on baths and showers should be considered to reduce temperature. These need to be placed as close to the point of use as possible.
170 To ensure the correct function of fail
…..temperatures under 50 C may increase the risk of Legionnaires’ disease, a form of pneumonia, due to bacterial growth in the tank. That disease is caused by Legionella bacteria, which live in water. Temperature is a critical factor for Legionella to grow. The risk of colonization in hot water tanks is significant between 40 and 50 C.
Legionella bacteria most often enter the lungs due to aspiration. (Aspiration means choking such that secretions in the mouth bypass the choking reflexes and enter the lung.) Drinking contaminated water is not a major cause of Legionnaire’s disease.
The Centers for Disease Control and Prevention estimates 8,000 to 18,000 Americans contract the disease annually. Five to 30 percent of the cases are fatal. While Canada has no national statistics, Hydro-Québec says about 100 people a year are hospitalized in that province for pneumonia caused by contaminated residential water heaters.
In homes with small children or elderly occupants, it may be appropriate to turn down the temperature of the hot water tank. For those who feel compelled to do so, the Canada Safety Council recommends a temperature no lower than 54 C. If you are unsure how to make the adjustment, hire a qualified professional such as a plumber to do the job.
Like other authors (3,4), including the World Health Organization (WHO) who published a recent monograph on the Legionella problem in drinking water (3), we believe that there is evidence for the transmission of legionellosis through the drinking water distribution systems in private homes. This is a serious illness associated with high death rates (up to 12%). Primary groups at risk (the elderly, smokers, the immunocompromised and patients suffering from chronic respiratory illnesses), are groups who include a large proportion of the population at home. Although we support prevention against tap water scalds, we are against setting water heater thermostats at 49°C because we believe this could facilitate proliferation of Legionella inside the tank and increase the risk of legionellosis.
In Québec, about 100 people a year are hospitalized for pneumonia caused by contaminated residential water heaters.
In light of the statistics, it is not advisable to lower the water heater temperature to, say, 49° C. This would not only reduce the hot water supply by some 20%, it would also put your household at risk of contracting pneumonia.
If anyone living in your home has a long term or serious illness, check with your doctor before turning down your water heater. Do not lower the thermostat setting of your water heater if anyone in your home has health conditions such as:
- chronic obstructive pulmonary disease
- an organ transplant
- a weak immune system (from disease or from taking medicine that suppresses the immune system).
For the prevention of Legionnaire’s disease, The World Health Organization recommends, “keeping hot and cold water systems clean and either keeping the hot water at 60°C and the cold below 20°C or alternatively treating them with a suitable biocide to limit growth.”
If you have any concerns about legionella, you can protect your family from tap water scalds by installing mixing valves instead. If there are individuals in the home with weakened immune systems, these are best placed at the tap and not at the exit from the hot water tank, since there is some risk that bacteria can grow in the warm water between the tank and the tap.