Top 5 Mistakes to Avoid During a Legionella Risk Assessment

A Legionella risk assessment is a vital part of ensuring the safety of water systems in any building, especially those accessed by the public, tenants, or employees.

These essential risk assessments help to identify potential hazards that could lead to the growth of Legionella bacteria. If the water systems become contaminated, then those who use the property are in danger of contracting Legionnaires’ disease, a serious and potentially fatal form of pneumonia.

But not all risk assessments are created equal, and with so much at stake, it’s important to know what a proper legionella risk assessment entails. Whether you’re a landlord, facilities manager, or business owner, avoiding common mistakes can mean the difference between compliance and liability.

Here we have put together the top five mistakes to steer clear of during a Legionella risk assessment,  as well as some useful and practical solutions to help put you on the path to a safe, compliant property.

1. Not Carrying Out an Assessment at All

It may sound obvious, but the biggest mistake that you can make is to not conduct a Legionella risk assessment in the first place.

UK law (under the Health and Safety at Work etc. Act 1974 and COSHH regulations) requires all landlords and business owners to assess the risk of exposure to Legionella. Simply assuming that your system is safe or low risk without a formal assessment can be a costly oversight, leading to serious legal and financial consequences for those responsible.

These repercussions include large fines, loss of business, prosecution, or even imprisonment under health and safety law. Beyond legal penalties, they may also face reputational damage and liability if someone becomes ill or dies as a result of exposure.

Solution – You should never neglect to carry out a legionella risk assessment; it should be a priority and something that is taken very seriously. Always make sure that you have a written risk assessment in place, even if your system is simple or used infrequently.

Performing a risk assessment will work to identify and manage any conditions in your water system that could support harmful bacterial growth, help to ensure legal compliance and protect the health and safety of anyone using the building.

2. Using Unsuitable or Inexperienced Assessors

A Legionella risk assessment should be carried out by a competent person with the required capability and sufficient understanding of water systems. Leaving the risk assessment to a person who has inadequate training or lacks the required experience and skills can be extremely dangerous and result in an incomplete or inaccurate report.

This not only leaves your property vulnerable but also provides a misleading sense of assurance, leading those responsible to believe that the building’s water systems are safe when in fact they are not.

Solution – Make sure that the individual you choose to carry out your legionella risk assessment is a competent person with the skills and knowledge needed to ensure it is done to an acceptable standard.

There is always the hugely beneficial and safer option of utilising the services of a professional legionella consultant to conduct your risk assessment. These specialists have the tools, skills, experience and credentials to take care of everything for you in a way that is convenient, reliable and cost-effective.

3. Failing to Review the Assessment Regularly

Many believe that once the risk assessment is done, it’s a “set and forget” task, when in reality, legionella risk assessments need to be reviewed regularly. This is especially true in circumstances where there have been alterations made to the water system or the buildings’ usage, purpose or occupancy levels have changed.

Without regular reviews, previously safe systems may develop new hazards that go unnoticed, leaving occupants vulnerable to exposure. Keeping the assessment up to date ensures that any emerging risks are identified and addressed promptly.

Solution – Be sure to schedule periodic reviews (usually annually) and reminders so that it is never forgotten or overlooked. You will also need to ensure that it is properly reviewed after any system changes, maintenance work, or reported concerns in order to remain compliant.

4. Overlooking ‘Low Use’ Areas

One of the most common oversights during a Legionella risk assessment is failing to account for areas with infrequent water use. Vacant flats, seasonal homes, infrequently used guest rooms, seldom-accessed showers, or disused pipework can easily be missed, yet they pose a significant risk.

When water sits stagnant in pipes or outlets for extended periods, it creates ideal conditions for bacteria to multiply, especially if the temperature falls within the risk range for Legionella growth, typically between 20°C and 45°C. These forgotten zones can undermine an otherwise well-maintained system, allowing hidden risks to persist unnoticed.