The law requires you to carry out a legionella risk assessment, but do you still need one if you’re not storing any water on-site? We explore here.

If your building does not store water, it is generally considered as a low-risk system, especially if cold water comes directly from the mains supply, and hot water through instantaneous heaters. 

What’s more, if the site is small, occupied by people who aren’t considered to be ‘at-risk’ of legionella (such as the elderly or those with compromised immune systems) and water usage during the day is frequent and travels through the entire system, then it too can be deemed a low-risk environment.

However, there are certain considerations that have to be made:

Are there any other risk systems?

The presence of certain equipment, also known as ‘systems’ could introduce complications to the site. An ‘other risk system’ could be any of the following, as described by HSE’s document HSG 274 Part 3:

• ultrasonic humidifiers or foggers;
• misting devices used for humidifying vegetables, meat and other food products;
• spray humidifiers;
• air washers, wet scrubbers, particle and trivial gas scrubbers;
• water softeners;
• emergency showers, eyebaths and face wash fountains;
• sprinkler and hose reel systems;
• spa pools;
• whirlpool baths;
• horticultural misting systems;
• vehicle washers including automatic washers for cars, buses, lorries and railway
• rolling stock;
• powered dental equipment;
• fountains and decorative water features including those on display for sale;
• non-disposable nebulisers used for respiratory therapy;
• industrial effluent treatment plants;
• irrigation systems;
• fire, dust and odour suppression systems;
• paint spray preparation equipment;
• tunnel pasteurisers and similar equipment.

The reason these systems are problematic for legionella control is due to the fact that many of them operate at, or can reach temperatures that allow the bacteria to grow.  In combination with this, they also produce a spray, known as an aerosol, giving any droplets of water containing legionella a way of being transmitted to humans via inhalation.  

The HSE makes it clear that the most challenging system for legionella risk is a spa pool, and has published an entire document with detailed guidelines on how to manage, control and prevent the bacteria from growing in these systems.  (See our blog for a summary of the document here.)

Are there any showers?

If your building has only toilets and washbasins, it is considered low risk – but if there are any showers, this risk is significantly raised, especially if it’s not maintained adequately.

To maintain showers, they must be cleaned and disinfected regularly. According to the HSE, flushing the shower should be carried out weekly, and disinfection on quarterly basis, at least. The latter will usually involve a six-step process:

1. Take apart the showerhead and hose;
2. Immerse these in a bucket with descaler;
3. Rinse away the descaler using fresh water;
4. Soak in disinfectant;
5. Rinse once again with fresh water.

It’s important that these procedures are performed with consistency, as any lapses can result in “a critical increase in legionella at the outlet”, as described by the HSE.  Therefore, clear records must be maintained after each control measure is carried out, so that building users are alerted to any occasions where it may not have been done.  

Conclusion: a legionella risk assessment is mandatory

Even if your system is as simple as it can be – that is, it doesn’t store water, there are no other risk systems and it doesn’t have any showers, carrying out a legionella risk system is still mandatory. In fact, it is a legal requirement, as duty holders must measure the likelihood of legionella and implement any control measures, if they are needed. For a low-risk system that is not storing water, however, it is probable that elaborate measures to control legionella risk will not be required. 

The legionella risk assessment is deemed to be complete once all risks are managed properly and deemed to comply with the law. However, it is the dutyholder’s responsibility to periodically review the assessment and it must be thought of as an ongoing process.

A new assessment must be performed if:

• There is a change to the water system or how the the building is being used;
• New information becomes available about legionella risks and measures;
• Monitoring checks reveal that control measures have become ineffective;
• The management team changes, for example there is a new dutyholder;
• There is an outbreak of legionnaires’ disease.

Do you want a quick way of checking whether or not you are compliant with legionella legislation? Download our free checklist here.