Legionella risk assessments are a legal requirement for many businesses in the UK — yet in practice, they’re often misunderstood, poorly managed, or treated as a one-off exercise.
Over the years, I’ve carried out assessments across a wide range of sites — from offices and schools to healthcare facilities and large commercial buildings — and the same issues come up time and time again.
Here are some of the most common mistakes companies make when it comes to Legionella risk assessments — and what you should be doing instead.
1. Treating the Risk Assessment as a “Tick Box Exercise”
One of the biggest issues is companies getting an assessment done purely to say they have one.
A Legionella risk assessment is not just a document to file away — it should be a working document that informs how your water systems are managed day to day.
If nothing changes after the assessment, or recommendations aren’t acted on, the risk hasn’t been properly controlled.
2. No Written Scheme of Control
This is a big one — and something I see regularly.
Many sites have:
- A risk assessment
- Some monitoring records
…but no written scheme of control.
This document is essential. It outlines:
- What needs to be done
- Who is responsible
- How often tasks are carried out
Without it, there’s no structured approach to managing Legionella risk — and this is a key requirement under UK guidance.
3. Recommendations Not Being Actioned
It’s very common to see the same issues appear on repeat assessments.
Typical examples include:
- Dead legs left in place
- Redundant pipework not removed
- Poor insulation
- Infrequently used outlets not managed
If recommendations aren’t addressed, the risk remains — and in some cases, increases over time.
4. Poor Temperature Control
Temperature control is one of the most important factors in Legionella prevention — yet it’s often overlooked or misunderstood.
Common problems include:
- Hot water not reaching 50°C at outlets
- Cold water exceeding 20°C
- Long pipe runs causing heat gain
- Systems not balanced correctly
If temperatures aren’t controlled, conditions can become ideal for bacterial growth.
5. Infrequently Used Outlets Ignored
Outlets that are rarely used — such as:
- Spare showers
- Little-used taps
- Seasonal areas
…can lead to water stagnation, which increases risk.
Flushing regimes are often:
- Not in place
- Not documented
- Not carried out consistently
This is a simple control measure — but one that’s often missed.
6. Systems Changed Without Review
Buildings evolve over time:
- Areas get refurbished
- Pipework gets altered
- Usage changes
But the risk assessment often stays the same.
If your system has changed, your assessment needs to reflect that. Otherwise, it no longer accurately represents the risk.
7. Over-Reliance on Contractors
While contractors play an important role, responsibility for Legionella control always remains with the duty holder.
I often see situations where:
- Monitoring is outsourced
- But no one on site understands the system
- Or checks that tasks are actually being completed
There needs to be oversight and understanding — not just delegation.
8. Lack of Training and Awareness
Even in higher-risk environments, staff are sometimes unaware of:
- Why controls are in place
- What temperatures should be achieved
- The importance of not altering systems
This can lead to:
- Heaters being switched off
- TMVs being adjusted incorrectly
- Controls being bypassed
Targeted training is key — especially for those responsible for the building.
9. No Ongoing Monitoring or Records
A risk assessment is only part of the picture.
You should also have:
- Temperature monitoring records
- Flushing logs
- Inspection records
- Maintenance logs
Without records, there’s no evidence that controls are being implemented — which can be a major issue in the event of an audit or incident.
10. Not Reviewing the Risk Assessment Regularly
Legionella risk assessments are not “one and done”.
They should be reviewed:
- Regularly (typically every 2 years)
- When systems change
- If there are issues (e.g. failed temperatures, positive samples)
An outdated assessment can give a false sense of security.
Final Thoughts
A Legionella risk assessment is only effective if it’s:
- Accurate
- Understood
- Actively used
The sites that manage Legionella risk well are not necessarily the ones with the most complex systems — they’re the ones with clear processes, good oversight, and consistent control measures.
If you’re unsure whether your current assessment is fit for purpose — or whether recommendations have been properly addressed — it’s worth reviewing your system before it becomes a bigger issue.
Need Support?
At Edge Water Hygiene, we provide practical, experience-led Legionella risk assessments that go beyond paperwork — helping you understand your system and stay compliant.
If you’d like a review of your current setup or need a new assessment, feel free to get in touch.
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