legionella bacteria in hot water system

All You Need to Know About Bacteria in Hot Water Systems

PropDid you know that the bacteria most commonly found in the humble water heater was genetically modified as a bioweapon in a science lab? Did you even know that bacteria can grow in hot water cylinders in the first place?

This often-overlooked appliance could be putting your family at risk. Don’t fear, Metropolitan Plumbing has everything you need to know about bacteria in hot water systems to keep your family safe.

Legionella Bacteria in Hot Water Heaters

The most common culprit found in a domestic hot water system is Legionella pneumophila.

Given the right conditions, you can find Legionella in water or soil. They live inside another microbe, amoeba, and are generally inhaled via contaminated water droplets in the air. You can even find these droplets coming out of air conditioning!

Once inhaled they can infect cells in your lungs and cause Legionnaires’ Disease or the less severe Pontiac fever. Thankfully, most Legionella infections only result in Pontiac fever. This is only exhibited as mild flu-like symptoms. It is usually resolved without treatment in 2-5 days.

Legionnaires’ disease, however, is much more serious. Severe pneumonia often accompanies it. In health and nursing home settings, the mortality rate from Legionnaires’ disease is as high as 40% according to the Department of Health’s Guidelines for Legionella control. For the immunocompromised, the young and the elderly, it is important they are not exposed to Legionella.

Water heater storage tanks are typically not the first choice for most bacteria. Given the right conditions, however, it can grow and even thrive in hot water tanks.

How Do I Get Rid of Bacteria In My Hot Water System?

Before you even receive your water it is treated by your water provider in the interest of public health. There are a few ways bacteria might find their way into your water, however:

  • Travelling from the supplier to you
  • Storing water at a dangerous temperature range
  • Faulty parts creating a false water heater temperature reading

We’re going to explain how and why bacteria might grow in your water heater and how you can reduce the risk of it growing and also get rid of it.

Water Treatment and Transport

Legionella and other bacteria are present in natural water sources before treatment. Some will usually remain post-treatment as well. Your supplier treats your drinking water supply with a disinfectant before delivering it to you.

This is because they tend to live in biofilms. These are a collection of different microbes in a membrane. This shelters some Legionella from the disinfectants and also provides it with nutrients to grow.

Disinfectants are used by your water supplier to kill bacteria present in water. Chlorine is the most common disinfectant, but there are several others available:

  • Heat
  • Chlorine dioxide
  • Copper-silver ionisation
  • UV light
  • Ozonation
  • Point-of-use microfiltration

Transporting it from the water supply to your home also has the risk of growing bacteria. This depends on the residual disinfectant, temperature and more.

Water Heater Temperature Setting

thermostat set to 63 degrees

We enjoy warm water for our showers, and bacteria like this very same warm water to multiply! For a water heater of the storage tank variety, you need to be especially careful about the temperature of your water.

You might think to set your hot water heater to a lower temperature to minimise the risk of scalding and save energy. This puts you at an increased risk of your tank growing bacteria!

Legionella bacteria thrive in temperatures between 20-45°c. Its most optimal temperature is 37-43°c.

When installing your water heater, your plumber will set the thermostat to heat your water to a minimum of 60°c. This is part of Australian building regulations to prevent bacterial growth in your hot water tanks.

In 60°c water, 90% of Legionella bacteria will die in 2 minutes. At 70°c, they all die nearly instantly!

Electric Water Heaters

Electric water heaters are at a greater risk of bacterial growth than other storage tanks due to their heating elements and uneven heating abilities.

Even with temperatures set to 60°c or above, many electric heater still contained Legionella bacteria. This was because the bottom of the tank was only reaching 30-40°c – the sweet spot for Legionella growth.

You can attribute the increased growth of bacteria in your water heater to these lower temperatures. This is why building regulations require the water temperature to be set to a minimum of 60°c to kill bacteria.

Tempering Valve

Hot water in the home suffers from a bit of the Goldilocks effect. Too high and you risk landing yourself with a nasty burn. Too low and now you’ve got a breeding ground for bacteria. Here to save the day is a tempering valve!

Tempering valves are a requirement for hot water systems in Australian residential homes. They only allow 50°c hot water in fixtures for sanitary plumbing, such as the shower or bathroom taps. They do this by mixing hot and cold water until it reaches 50°c.

These valves became mandatory as a way to prevent scalding from water that is too hot. At 50°c, both adults and children can comfortably enjoy a shower for approximately 5 minutes before it starts burning.

Thermostatic mixing valves (TMVs) perform the same job but offer greater accuracy. Nursing homes, child daycares, and other similar businesses use TMVs for their more accurate 50°c hot water.

While 50°c is not in the danger zone, it is not in the optimal water temperature to kill Legionella bacteria. Proper maintenance and regular flushing of any tempering valves helps to prevent the growth of harmful bacteria, and is therefore an important process.

Flush the System

If your plumbing system isn’t set up correctly, there may be regions where water pools and becomes stagnant in your pipes. The temperature of the water is uncontrolled here and might be prone to bacteria growth. Mineral deposits can also build up in your water heater, pipes, fittings and taps affecting your water pressure and leading to other plumbing problems

You should flush your plumbing system regularly to remove any bacteria and build-up. Better yet, a plumber should repair areas where water stagnates in the first place.

Should you find bacteria in your plumbing system, not only should you flush the hot water heater itself, but all associated fittings too.

Regular Services

You can have the temperature set correctly to 60°c and have the system flushed regularly but without regular servicing of your water heater and general plumbing, there might still be bacteria growth.

If the thermostat is faulty, for example, your water isn’t heating as it should. Without the trained eyes of a plumber, who knows how long the temperature will be off the 60°c and allowing bacteria to grow?

How Do You Test For Legionella in Water?

scientist with bacteria culture assay under microscope

When it comes to testing for Legionella and other bacteria in a hot water tank, you’re best leaving it to the professionals. Biological scientists take multiple samples across your plumbing system to assess the levels of bacteria there are.

They have a variety of different tests they might use to identify bacteria, each with certain pros and cons:

  • Culture methods – cost-effective and well understood, but time-consuming
  • Immuno-agglutination – identifies different strains of bacteria but requires existing growth, typically from the previous cultures
  • Quantitative polymerase chain reaction – very precise reporting and quick results but doesn’t differentiate between strains
  • Rapid DNA assay – Equally as accurate as culture methods and it is faster but has limited availability

So long as you’re taking care of your hot water system and following Australian regulations for water temperatures, you do not need to worry about the growth of Legionella in your water heater.

Alternatively, ditch the old storage tank and opt for a continuous-flow water heater. Not only do these not run the risk of growing bacteria, but they’re also more energy efficient!

To find out more about what to do about bacteria in hot water systems from a licensed plumber, contact Metropolitan Plumbing.


Published: 2020-08-03

Need a Plumber Today?

Electrical, plumbing and air conditioning work is essential and we will be available to do the jobs you require in your home. Our friendly technicians are taking all precautionary measures and keeping to best hygiene practices.

Plumbers You Can Trust

Our Promise to You

Honest Plumbing Services Icon

Honest

We believe in transparency. We will guide you through our process, answer your questions and provide you with an upfront, no obligation fixed prices.

Committed to Plumbing Service Excellence Icon

Committed

No matter how big or small the job is, whether you're a new or returning customer, we treat every job as important and strive for success.

Professional Expert Plumbers Icon

Professional

We know our job site is your home and we completely respect that. We arrive neat and clean, and tidy up after we've completed the job.

zip pay Options
Zip Pay Payment Options Image

Now Available!

Plumbing finance options** with trusted pay later options

What Our Happy Customers Have to Say

This is why we do, what we do!

Metropolitan Plumbing are proud winners of 2021 and 2020 Product Review awards in the plumbing category. These awards highlight our dedication to outstanding customer service. Product Review provides a platform for real-life experiences. Check out some of our customers' reviews below:
5 stars rating

Dave.C was very friendly and professional especially for a Sunday. He was able to identify the cause of the leaky shower head, and provide two quotes. He was also able to show what the issue was and was able to advise what he had done to fix it. Thank you.

Tyrell Tongz - QLD
5 stars rating

They replaced our old, malfunctioning toilet. The installation was quick, and they checked for any leaks thoroughly. Reliable service we can count on!

Anna Cunning - QLD
5 stars rating

I had a toilet that wouldn’t stop running, and it was wasting so much water. They arrived promptly, diagnosed the issue, and replaced the faulty parts. Now my toilet works perfectly. Great service and reasonable rates.

Caity Waters - QLD
  • Wilson Hot Water Logo

    Wilson is an Australian owned and operated hot water system supplier with products to suit any need. Rest assured our technicians can install and service your Wilson hot water system.

  • Vulcan Hot Water Logo

    Vulcan hot water systems are forged tough so that they can handle Australia's changeable climate without missing a beat.

  • Thermann Hot Water Logo

    Thermann is one of the most efficient water heating systems around, with a range of options from solar boosted to heat pumps. We can install, service and repair your Thermann system.

  • Saxon Hot Water Logo

    Unfortunately, Saxon no longer produces heating units, but Metropolitan can still service, repair or replace your old Saxon system.

  • Stiebel Eltron Hot Water Logo

    Stiebel Eltron was established in Germany, 1924. With over 95 years of experience in making hot water units, you can expect quality.

  • Rinnai Hot Water Logo

    Rinnai is one of the biggest names in hot water systems. Metropolitan Plumbing has worked with Rinnai hot water systems for more than 25 years.

  • Rheem Hot Water Logo

    Rheem has been going steady, hot and strong since 1939 with a comprehensive range of solar, heat pump and gas hot water solutions.

  • Everhot Hot Water Logo

    No matter how big or small your requirements are, Everhot has the right system. We at Metropolitan can help install or service your Everhot system.

  • Edwards Hot Water Logo

    Edwards is recognised for its superior performance and outstanding range of ground and roof mounted units offered in a range of colours.

  • Dux Hot Water Logo

    Dux is the big name in residential and commercial solar, heat pump and gas water heating. We can service and repair your Dux hot water system.

  • Chromagen Hot Water Logo

    Chromagen is an internationally recognised manufacturer of highly efficient hot water systems.  Metropolitan can service, replace or repair your Chromagen system.

  • Bosch Hot Water Logo

    Bosch provides quality hot water to thousands of Australians with its wide range of solar, gas and electric units.

  • AquaMAX Hot Water Logo

    AquaMax is the household name in hot water. We can take care of all of your Aqua Max needs from installation to repair.

Metropolitan Plumbing - Product Review img Metropolitan Plumbing - Product Review img