What to Do in a Legionella Outbreak – A Practical Guide for Duty Holders

When you’re responsible for a property or business premises, hearing the words “Legionella outbreak” can be alarming. But acting quickly, correctly, and in line with UK guidance can protect people and minimise disruption.

Whether you’re a facilities manager, landlord, or responsible person under ACOP L8, this blog will walk you through the practical steps to take during a suspected or confirmed legionella outbreak.

1. Understand What a Legionella Outbreak Is

A legionella outbreak refers to two or more confirmed cases of Legionnaires’ disease with a common source – typically linked to the same building, water system, or cooling tower. It can also be used more broadly when anyone becomes ill and there’s a suspected link to waterborne legionella bacteria on your premises.

Legionnaires’ disease is a severe form of pneumonia, usually contracted by inhaling tiny droplets of contaminated water. That’s why misting from showers, taps, fountains, or cooling towers poses a risk.

2. Stop Activities That May Expose Others

The first action in a suspected outbreak should be to stop any water system activities that may generate aerosols, such as:

• Turning on showers, spray taps, or decorative fountains
• Running air conditioning or cooling systems connected to water
• Allowing public or tenant access to areas with potential exposure

This helps prevent further spread until the source is identified and addressed.

3. Inform the Right People

Even if it’s just a suspicion, it’s your duty to inform relevant parties immediately:

• UKHSA (UK Health Security Agency) – if someone has been diagnosed with Legionnaires’ and your premises may be the source, the local Health Protection Team must be contacted.
• Local authority environmental health team – especially in public buildings, leisure centres, hotels, and care homes.
• Tenants or staff – keeping people informed reduces panic and protects your reputation.

If your site falls under COMAH (Control of Major Accident Hazards) or has a cooling tower, there are additional reporting requirements.

4. Call a Professional Legionella Specialist Immediately

Time matters. Don’t try to resolve the outbreak alone.

You’ll need an experienced water hygiene company (like H2O Comply) to:

• Conduct a full site risk assessment
• Review existing control measures and logs
• Collect microbiological water samples for lab testing
• Help isolate potential sources of contamination
• Advise on or carry out urgent remedial action

UKAS-accredited sampling and swift turnaround times can make all the difference when people’s health and legal responsibility are at stake.

5. Undertake Emergency Remedial Works

Depending on the outcome of the site survey and sampling, actions may include:

• System disinfection or chlorination
• Thermal flushing (running hot water at 60°C or higher through systems)
• Dead leg removal
• Showerhead and TMV cleaning or replacement
• Repairs or updates to the water storage tank

Documentation of all corrective actions is essential to demonstrate compliance if HSE or Environmental Health investigate.

6. Review and Update Your Control Measures

Once the immediate risk is removed, you need to ask: how did this happen?

• Was the risk assessment out of date?
• Were routine checks or maintenance missed or done incorrectly?
• Were recordkeeping or staff training lacking?
• Were any parts of the system left unused for too long, leading to stagnation?

This is your chance to prevent future recurrence, improve your management plan, and ensure you’re fully compliant with the Health and Safety at Work Act, COSHH, and ACOP L8.

7. Communicate Reassurance and Reopening

Once the water system is declared safe:

• Reopen water outlets gradually, following guidance
• Keep tenants, guests, and staff informed of what happened and how you resolved it
• Provide evidence of clearance sampling and remedial work

Transparency matters, especially for public-facing businesses like leisure centres, hotels, and gyms.

8. Ongoing Monitoring and Maintenance

After an outbreak, you’ll want more than basic compliance – you’ll want peace of mind. We recommend:

• Increasing the frequency of temperature checks and sampling
• Regular tank inspections and TMV servicing
• Remote temperature monitoring, especially in high-risk or multi-site setups
• Professional Legionella training for site staff

Prevention is always easier – and cheaper – than crisis management.

Final Thoughts

A legionella outbreak doesn’t just affect systems – it affects people, reputations, and trust. With fast action, expert support, and long-term prevention measures, you can protect your premises and everyone in it.

Need Immediate Legionella Support?

If you suspect an outbreak or want to improve your legionella control plan, H2O Comply is here to help. We offer:

✅ Emergency response site visits
✅ BS8558-compliant disinfection
✅ Legionella risk assessments
✅ Water sampling & UKAS lab testing
✅ Ongoing monitoring and training

📞 Call us now or contact us online – we’ll get you back on track fast.