Introduction
Legionnaires’ disease isn’t just a concern for hospitals or industrial buildings — it can happen in ordinary homes, especially when hot water systems aren’t maintained correctly. In Queensland, where warm weather and solar systems are common, the risk is particularly real. In this article, we’ll break down what Legionnaires’ disease is, why water temperature matters, and how you can keep your household safe with the right hot water settings.
What Is Legionnaires’ Disease?
Legionnaires’ disease is a serious type of pneumonia caused by Legionella bacteria. These bacteria thrive in stagnant, warm water and are commonly found in:
- Hot water systems
- Showerheads
- Spa baths
- Garden hoses and potting mix
The disease is contracted by inhaling mist or vapour that contains the bacteria. It is not spread from person to person or by drinking infected water. Symptoms often include high fever, cough, muscle aches, and difficulty breathing. If untreated, it can lead to hospitalisation or even death, particularly in older adults or those with weakened immune systems.
Queensland-Specific Cases
Queensland has seen a rise in Legionnaires’ cases, especially due to warm conditions and widespread use of solar hot water systems.
- 2022 Spike: Queensland recorded 88 cases of Legionella longbeachae infections, triple the average from 2017–2021, mainly linked to potting mix and soil (ABC News).
- 2025 Case in Townsville: A case confirmed in April 2025 involved a patient believed to have contracted Legionnaires’ disease while travelling. No local cluster was found, but it raised awareness across the region.
These numbers highlight the need for regular inspection and correct temperature settings of home water systems.
How Legionella Bacteria Thrive
| Water Temperature | Legionella Risk |
|---|---|
| 0°C to 20°C | Dormant but can survive |
| 20°C to 45°C | Ideal growth zone |
| 50°C | Bacteria start dying |
| 60°C and above | Bacteria killed quickly |
To minimise risk, water stored in your system should be kept above 60°C, even though tempering valves will reduce the delivery temperature at taps to around 50°C for safety.
Common Mistakes That Increase Risk
Many households are unaware that small changes to their hot water setup can create an environment for Legionella to thrive:
- Turning system temps down to save energy
- Rarely using guest bathrooms or outdoor showers (stagnant water)
- Systems over 5 years old without maintenance
- Sediment buildup in tanks providing bacteria a place to hide
- Solar or heat pump systems that don’t cycle hot enough regularly
- Improper installation that creates “dead legs” in pipework (sections of pipe with no water flow)
Busting the Myths
Some people believe cold showers or flushing pipes occasionally is enough. It’s not. Here’s why:
- Legionella lives in the system, not just at the tap or showerhead.
- It’s inhaled as vapour, not drunk, so even water that feels safe might be risky.
- Lowering temps to save money can have unintended health consequences.
What Queensland Health Recommends
Australian Standard AS 3500 and QLD regulations recommend:
- Storage temperature at least 60°C
- Delivery temperature no higher than 50°C to prevent scalding (via tempering valve)
- Annual servicing for older or solar systems
Failing to comply with these recommendations could lead to not just health issues, but potential liability for landlords or property managers.
What Happens During a Hot Water Safety Check?
A licensed plumber (like the team at RJT Plumbing and Gas) will:
- Check temperature at the tank and taps
- Inspect the tank for scale or sediment
- Test the tempering valve
- Identify stagnant lines or poor circulation
- Advise on system age, efficiency, and compliance
Visual Reference: Safe Water Zones
Signs You May Need an Inspection
- Your hot water isn’t as hot as it used to be
- System is older than 5 years
- You haven’t had a service in 12 months or more
- You’re a landlord and unsure of compliance
- System is solar or heat pump based
FAQs
Can I just turn my hot water up myself?
Some systems allow user adjustment, but others require a plumber. Be cautious not to override tempering valves or compromise safety.
Is Legionnaires’ disease really that serious?
Yes. It can result in hospitalisation and even death, particularly in older or immunocompromised people.
I have a solar hot water system – is that a risk?
It can be if not maintained. Some solar systems don’t reach 60°C unless regularly boosted.
Do I need a tempering valve?
Yes, it’s required by law to protect against scalding.
Call to Action: Protect Your Home
With cases on the rise and the risk clearly documented in Queensland, ensuring your hot water system is set correctly is a vital health precaution.
RJT Plumbing and Gas offers:
- Hot water system inspections
- Compliance checks for landlords
- System upgrades and maintenance
Get peace of mind today. Contact RJT Plumbing and Gas to book your hot water safety check.
Final Thoughts
Legionnaires’ disease might sound like a rare issue, but it’s a growing concern in modern households that neglect system maintenance. Don’t leave it to chance. Check your settings, stay compliant, and protect your family.
This article is provided as general advice and does not replace professional inspection or servicing. Always consult a licensed plumber.
