What Landlords Need to Know About Legionella

A new wave of property upgrades is sweeping the UK. Fuelled by sustainability goals, government grants, and the drive toward net zero. One of the most popular upgrades? Heat pumps.

But beneath their eco-friendly exterior lies a quiet, often overlooked health risk: Legionella bacteria.

Low water temperatures common in heat pump systems may increase the risk of Legionella growth. Especially in poorly managed or ageing buildings.

At The HSRA, we’re urging landlords, facilities managers, and duty holders to understand the implications. By taking proactive steps, they can protect both occupants and investments.

Why Are Heat Pumps Under Scrutiny?

Heat pumps are designed for efficiency, often heating water to 50–55 °C rather than the traditional 60–65 °C used in gas systems. While this reduces energy use. It brings a building’s hot water system dangerously close to Legionella’s ideal growth range. Which thrives between 25 °C and 45 °C.

Key Risk Factors:

• Lower hot water temperatures that don’t reach disinfection levels
• Stagnant or underused outlets, such as showers or taps in guest rooms or seasonal buildings
• Infrequent maintenance or testing, especially in properties without formal compliance protocols

A Quick Refresher: What is Legionella?

Legionella is a naturally occurring bacterium found in water systems. It can occur in taps, showers, or HVAC systems and can cause Legionnaires’ disease, a severe and sometimes fatal form of pneumonia.

Those most at risk include: People over 45, smokers & individuals with respiratory or immune conditions

Even one case traced back to a commercial property can result in HSE investigations, legal action, and reputational damage.

Heat Pumps & Legionella: What Should Landlords Do?

The shift to greener heating solutions must not come at the cost of occupant safety. Here's how to mitigate risk:

1. Review Water System Temperatures

Ensure that systems heat water to 60 °C or higher. Either continuously or via periodic “pasteurisation” cycles.

2. Update Your Legionella Risk Assessment

Include system design reviews. Temperature mapping. Flow pattern analysis, and flushing protocols.

3. Implement Ongoing Monitoring

Monthly temperature checks. Quarterly inspections, Annual reviews, and Legionella testing every 6–12 months.

4. Educate Maintenance Teams

Ensure staff or contractors understand the interaction between low-temperature systems and biological risk.

Who Needs to Take Action?

This warning applies to Landlords of HMOs and flats. Care homes and sheltered housing schemes. Schools and nurseries. Hotels, guest houses, and Airbnbs. Anyone running a commercial building operating with heat pump systems. Even small commercial properties or student lets are at risk if water systems are not maintained correctly.

HSRA’s Role: Stay Compliant, Stay Protected

At HSRA, we conduct independent Legionella risk assessments across England, Wales, and Scotland. Helping to ensure your property remains safe, compliant, and prepared for inspection.

Our assessors are trained to evaluate modern heating systems.

All assessments include:
- On-site inspection
- Temperature profiling
- Asset condition review
- Action plan with prioritised steps
- Support with ongoing monitoring or provision of water testing kits

Book Your Legionella Assessment Today With The HRSA