Introduction

Legionella bacteria can pose a serious health risk in water systems — especially in buildings with complex plumbing.

One of the most effective ways to control it is temperature control.

But what temperature actually kills Legionella?

In this guide, we break down the exact temperatures you need to know, based on UK guidance, and how to stay compliant.

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🌡️ What Temperature Kills Legionella?

Legionella bacteria begin to die at temperatures above 50°C.

• 50°C → bacteria start to die
• 60°C → most bacteria killed within minutes
• 70°C+ → bacteria killed almost instantly

👉 This is why hot water systems are typically stored at 60°C or higher.

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❄️ What Temperature Does Legionella Grow At?

Legionella thrives between:

• 20°C – 45°C

This is known as the danger zone.

• Below 20°C → bacteria become dormant
• Above 50°C → bacteria begin to die

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📏 UK Temperature Guidelines (HSE)

To control Legionella, UK guidance recommends:

• Hot water stored at: 60°C
• Hot water at outlets: ≥50°C within 1 minute
• Cold water: ≤20°C

👉 These are critical compliance benchmarks during monitoring.

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⚠️ Why Temperature Control Is So Important

Poor temperature control is one of the most common failures found during Legionella risk assessments.

Issues often include:

• Hot water not reaching 50°C at outlets
• Cold water warming above 20°C
• Dead legs allowing stagnation
• Oversized systems

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🔧 How to Maintain Safe Temperatures

Practical steps include:

• Regular temperature monitoring
• Insulating pipework
• Removing dead legs
• Maintaining calorifiers
• Ensuring good water turnover

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🏢 Where Temperature Control Matters Most

High-risk environments include:

• Hotels
• Hospitals
• Care homes
• Leisure centres
• Office buildings

Anywhere with stored or recirculated water systems.

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📋 Legal Responsibilities

UK duty holders must control Legionella risk under:

• Health and Safety at Work Act
• COSHH Regulations
• HSE ACOP L8

Temperature control is a key compliance requirement.

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✅ Final Thoughts

Understanding what temperature kills Legionella is fundamental to managing risk.

Keeping water outside the 20°C – 45°C danger zone is one of the simplest and most effective control measures.

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📞 Need Help Managing Legionella Risk?

At Edge Water Hygiene, we carry out compliant Legionella risk assessments and system reviews across the UK.

👉 Contact us today for expert advice.