AccuServ Heating and Air Conditioning

Legionnaires’ disease

January 3, 2020

What is Legionnaires’ disease?

Legionnaires’ disease is a form of pneumonia with all the related symptoms: fever, muscle pains, and constant shaking. A fatal disease, Legionnaires’ disease can be contracted directly from your water system if not properly maintained.

How? Legionnaires’ disease spreads through a form of bacteria known as legionella, which love to live in contaminated water (i.e., water in which hazardous materials were introduced to the water sometime after leaving its source). If your water system is not properly maintained, it might become a home to legionella, placing you and your family in danger.

Is it common?

In Canada, we see about 100 episodes of Legionnaires’ disease per year, though this figure is thought to be an underestimate.[1] However, the fact that it is fatal and has a 5% exposure-to-illness rate means you certainly do not want to ignore this danger. This goes double for high-risk groups, such as the elderly.

Why would my home have contaminated water?

Legionella are actually quite prevalent, being found in natural bodies of water in harmless quantities. It should be no surprise that home water systems should also have harmless quantities of this bacterium. The danger is when Legionella are allowed to multiply at a dangerous rate within a water system that is particularly hospitable.

Because your home water system is much more complex than a natural pond, Legionella have an enhanced ability at moving throughout the system, spreading quickly and moving to hospitable spots. What is a “hospitable spot?”

Legionella multiply quickly when they:

  • Live in water at a temperature of 20C (68F) to 45C (113F)
  • Have access to “contamination” within the water – rust or lime, which can be common in improperly maintained water systems

Thus, your water tank could very well fit the needs of a growing Legionella population, which might then spread to you and your family through your shower, tap, or sprinklers.

How do I prevent Legionnaires’ disease?

As you might have guessed, prevention of the disease is simply denying the Legionella one of the two previously mentioned requirements for multiplication. Thus, you have two options:

  • Ensure your water is always below 20C (68F) or above 45C (113F).
  • Remove any contaminates from your water system.

In brief, this means that hot water should be heated to above 45C (113F). When you are not using hot water, the water should be cooled to under 20C (68F). Of course, homeowners will likely be consistently running their hot water heaters, making the latter action impractical; instead, just ensure that your hot water heater is consistently above 45C (113F), at which point 90% of the legionella is killed within 2 hours.

Removing contaminates means to ensure your water system is constantly flowing, preventing the stagnation of water that ultimately leads to impurities.

What specific actions can I take?

Your safest action is to simply keep your water at a temperature high enough to kill all the Legionella. But if you’re especially concerned with the bacteria, test your water system for Legionella. If you find the bacteria in your water, you will need to disinfect the entire water system. You will also want to find the reason for the Legionella so as to avoid future risk (e.g., Were you not running your water enough? Or perhaps your water was not hot enough? Maybe one of the components in your water tank was rusted, causing contaminants.)

Most crucial of all is to be aware of all the possible risks of Legionnaires’ disease. Ask yourself of other ways that might expose you to Legionella. For example, if you run an external Jacuzzi, disinfect your Jacuzzi water often.

What about my hot water tank?

Because Legionella prefer to live and multiply in water below 45C (113F), you should ensure your hot water tank stores water at above that temperature. Going well above the ideal living conditions for Legionella by heating your water tank to, say, 60C (140F), you can be confident that the majority of the Legionella living in it will be killed.

Regardless of whether you’re running an electric, gas, or combi water heater, you want to ensure that the water is getting hot enough to prevent Legionella growth. So, set your water heater tank to 60C (140F). Alternatively, call a professional to do it for you.

That said, if you have a tankless water heater installed instead of a conventional water heater, you do not have to worry. The main threat Legionella pose is their buildup in the calcium deposits of a water heater tank. If you do away with the tank, you do away with the Legionella. Contact your local HVAC company to learn more about tankless water heaters.

Isn’t 60C (140F) too hot for use?

So you don’t want to take 60C (140F) showers but you also don’t want the risk of Legionella breeding in your water heater. Isn’t there a middle ground? The answer goes back to how your hot water tank works.

Yes, 60C shower water is dangerous (it can scald), but when that scalding hot water in your hot water tank will be dispersed to your tap and showers, the ultimate temperature will not be 60C (140F) because of the mixing valves installed in your domestic water system. As its name suggests, the mixing valve mixes the 60C (140F) water with cold water to bring the temperature to a comfortable degree. Hence, you can keep your water tank’s internal temperature at a safe and hot degree while supplying your tap and shower with comfortably warm water.

You can change the temperature of the domestic water with the mixing – or tempering – valve. Call a specialist if you need help with this, especially if you have recently raised the temperature of your tank’s internal hot water.

Any other concerns?

The thought of Legionnaires’ disease is unlikely to be constantly on your mind, so when you are looking for ways to cut down on your home’s energy costs, you might think turning down your water heater’s thermostat is a good way to save on energy costs. Unfortunately, you are increasing your risk of exposure. Fortunately, you have other ways to save on energy costs (see the next section).

In addition, misunderstandings on the other side of the spectrum should also be stressed. That is, you might shut off your hot water tank, expecting the water to fall below 20C (68F), which is a safe temperature, protecting against Legionella. However, the summer could easily keep your water tank’s internal water at the perfect temperature for Legionella – especially if your water tank is external, exposed to sunlight.

Then there’s the issue of rust or other contaminates. You should have a professional give your water tank regular inspections to ensure it does not contain such risk factors. In addition, a professional can also find malfunctioning parts that might be causing the thermostat temperature and true internal temperature to be out of sync.

Are electric water heaters especially at risk?

Yes! One Canadian study has shown that the ownership of an electric water heater (as opposed to a gas or combi heater) is related to an increased risk of Legionnaires’ disease.[2] The reason was that the thermostat of an electric water heater is often wrong. While you might have set your electric water heater’s thermostat at 60C (140F), the truth is the water is not evenly heated, causing some spots of the internal water to be at just the right temperature for Legionella multiplication.[3]

An easy solution is to switch from an electric heater to a gas heater. A side benefit of this would be reduced energy costs, as gas water heaters – while more expensive upfront – will save you money in the long term due to the lower cost of each energy unit. Another option is a combi boiler, which typically also use gas and carry additional benefits.

Then there’s the tankless water heater. Without a tank, this water heater offers Legionella no place to reproduce. This allows you to bypass the 60C (140F) rule, which in turn can help you save money.

Call us today to learn more about these options.