Posted on 07/05/2009 9:59:53 PM PDT by Chet 99
For your homes you should protect against scalding (especially if small children or elderly are in the home), but also against Legionella.
Few points...
1. First, it was clearly Fahrenheit, not Celsius. Nevertheless, scalding can occur quickly.
2. By contrast, if the water is kept too low, Legionella becomes a possibility.
A brochure, 33 Questions and Answers: Water Safety and Tempering (PDF), from the Watts Regulator Company covers the challenge. The solution is to keep the storage water temperature at 145 deg F or higher to kill Legionella (of course, temperatures this high increase your carbon footprint... darn) and to use a mixing valve to restrict the temperature of water delivered from the faucet or showerhead to 120 deg F. Here are some excerpts...
What is Legionnaire’s Disease?
Legionnaires’ disease is a lung infection (pneumonia) caused by a bacterium named Legionella pneumophila. The name Legionella pneumophila was derived from the original outbreak at the 1976 American Legion Convention in Philadelphia. A total of 221 people contracted the disease and 34 died.
What is the incidence of Legionnaires Disease?
According to the Center for Disease Control, between 8,000 and 18,000 people are hospitalized with Legionnaires’ disease in the U.S. However, many infections are not diagnosed or reported, so this number may be higher. More illness is usually found in the summer and early fall, but it can happen any time of year. OSHA states, because it is difficult to distinguish from other forms of pneumonia, many cases go unreported. They estimate over 25,000 cases of the illness occur each year and cause more than 4,000 deaths.
What is the relationship between water temperature and Legionella survival?
Legionella can survive in a wide range of conditions, including temperatures of 0° to 63°C (32° to 145°F) , and pH of 5.0 to 8.5. Temperature is a critical determinant for Legionella proliferation. Colonization of hot water tanks is more likely if tank temperatures are between 40 and 50°C (104 to 122°F). Legionella and other microorganisms become attached to surfaces in an aquatic environment forming a biofilm. Legionella has been shown to attach to and colonize various materials found in water systems including plastics, rubber, and wood. Organic sediments, scale, and inorganic precipitates provide Legionella with a surface for attachment and a protective barrier.
In a recent nationwide survey of guest room water temperature in hotels, what percentage of rooms did the hot water temperature exceed 125°F and 140°F?
In an ongoing survey conducted by Watts Water Technologies that includes over 350 hotel stays, at 52 hotel chains and independents in 41 states, 53.1% of hotels delivered hot water in excess of 125°F at the shower and 61.9% at the lavatory. 12.2% of stays recorded water in excess of 140°F at the shower and 9.7% at the lavatory. At 140°F, it takes only three seconds to sustain a first degree burn and five seconds to sustain a third degree burn.
According to the same survey, the average maximum water temperature recorded in the shower and lavatory for 350 rooms was:
124.8°F and 127.0°F respectively. Maximum temperature was measured by turning shower valves and lavatory faucets to their full hot position, and then maximum outlet temperatures were recorded.
What is The Center for Disease Control’s (CDC) recommendations for minimizing the risks of Legionella and scalding in relation to domestic water temperature settings?
The Guidelines for Environmental Infection Control in Healthcare Facilities, Recommendations of the CDC and HICPAC, published by the U.S. Department of Health and Human Services states, “cold water in healthcare facilities should be stored and distributed at temperatures below 68°F, hot water should be stored above 140°F and circulated with a minimum return temperature of 124°F, or the highest temperature specifi ed in state regulations and building codes. If the return temperature setting of 124°F is permitted, then installation of preset thermostatic mixing valve near the point-of-use can help prevent scalding”.
What OSHA’s (Occupational and Safety Health Administration) recommendations for minimizing the risks of Legionella and scalding for hot water distribution?
According to the OSHA Technical Manual on Legionnaires disease (Section 3:Chapter 7), “To minimize the growth of Legionella in the system, domestic hot water should be stored at a minimum of 60°C (140°F) and delivered at a minimum of 50°C (122°F) to all outlets. The hot-water tank should be drained periodically to remove scale and sediment and cleaned with chlorine solution if possible. The tank must be thoroughly rinsed to remove excess chlorine before reuse. Eliminate dead legs when possible, or install heat tracing to maintain 50°C (122°F) in the lines. Rubber or silicone gaskets provide nutrients for the bacteria, and removing them will help control growth of the organism. Frequent fl ushing of these lines should also reduce growth. Domestic hot-water recirculation pumps should run continuously. They should be excluded from energy conservation measures.”
Call a plumber and get a mixing valve installed in your home.
And no, I'm not in the employ of Watts, have no partnership with them, do not get a dime from them, yada, yada. Darn it.
However, if I was subject to a nice profit motive, it would not make the truth less true, nor would it taint me. People with a profit motive are honest. Without a profit motive, I tend to suspect a power motive, as in a desire for power over my life and liberty.
“Call a plumber and get a mixing valve installed in your home.”
I’ve never been able to set one of them where the water was hot enough to suit me!
If my skin isn’t red when I get through with a shower the water wasn’t hot enough!
/johnny
You missed a /s.
But it was funny, and I don't care what lights you black out when you fire up the welder.
/johnny
We had two main water heaters that were steam operated. One was for patients use including the showers it was low temp the other was for laundry and kitchen and it was at 180 degrees. We had to have it licensed. In my state the regulations say water temps have to be about 110 or below for patient use. There were mixing valves in the showers but not on the sinks.
Faucets have always had plastic or rubber parts in them. The article is a little bit overkill as there is no way to prevent water use at lower temps. IOW you are going to use sprayers etc and the end temp will be what you can tolerate.
I'm a country boy living off well water stored in a water tank next to my well. You stand a far better chance of getting a disease from surface water run off or a well too close to sewage etc than you do catching Legionaries. Some places like commercial A/C the prevention makes sense and is practical to do. In other places it's impractical and overkill.
No better testing ground I can think of to say the risk is very minimal than the United States Navy Ships. Water is produced in temps well above 110 degrees and piped throughout spaces as hot. Storing potable cold tap water in any enviroment residential or otherwise and distributing it below 68 degrees is not practical period with the exception of a water fountain maybe. Then you stand a far better likely several hundred fold chance of catching a flu virus off the water fountain. :>}
My friend contracted Legionaires from what we think was molded air vents. The house he had rented had been flooded a few years before and the vents were never cleaned. Now his kidneys are nearly completely shut down and he has to undergo dialysis twice a week.
I believe that legionella requires a certain amount of stagnation that won’t occur with normal household use.
It is rare in plumbed potable systems as opposed to cooling systems.
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