Dental mythbuster 5: Legionella and dental waterline management

HTM 01-05: Decontamination in primary care dental practices states that, “Registered Managers of dental practices have an overriding general duty of care under the Health and Safety at Work Act 1974”. 

Part of this duty of care is to ensure that the water supply, storage, and distribution services should comply with best practice guidance:

• Legionnaires' disease. The control of legionella bacteria in water systems: Approved Code of Practice and Guidance L8, Health and Safety Executive (ACOP L8)
• Legionnaires' disease. Part 2: The control of legionella bacteria in hot and cold water systems. Health and Safety Executive
• HTM 04-01 Safe water in healthcare premises

Legionella bacteria and other organisms live in water supplies. Some are harmless, but others cause disease. These organisms form 'biofilms' quickly in dental waterlines because:

• there is a source of nutrients for the bacteria
• plastic tubing in waterlines contains ‘plasticisers’
• temperatures in the surgery can warm the water
• water in the system can remain stagnant overnight and at weekends.

Research shows that bacterial counts in waterlines can be very high. Contaminated dental unit waterlines can expose patients and staff to harmful aerosols. Patients who may be more vulnerable could be at increased risk of respiratory infections when they inhale these contaminated aerosols during treatment.

Mandatory requirements

Your practice must meet the following specific requirements:

1. All systems require a risk assessment, though some may only need simple control measures.
2. All premises are required to have a written waterline management scheme and legionella risk assessment. Experienced and competent people should write these schemes. A competent person is someone with the necessary skills, knowledge, and experience to carry out this function.
3. The registered manager must implement all recommendations from the scheme and risk assessment.
4. Water and air lines must have anti-retraction valves fitted in accordance with EU regulations.
5. You must control legionella within the dental waterline system, though no single treatment is completely effective.

Recommended practice

Maintaining dental waterlines

Different products are available to disinfect waterlines, but not all products completely remove biofilm. Staff should follow the manufacturer’s instructions to control the bacterial count. 

Waterlines should be flushed regularly along with using these products. 

Staff should also review the manufacturer’s instructions for the dental chair unit, as some manufacturers do not recommend using specific products. 

HTM01-05 guidance suggests a typical regime for maintaining dental waterlines.

Frequency of testing 

Apart from situations where there are taste or odour problems, it is not necessary to carry out routine microbiological monitoring for total viable counts in dental waterlines. 

How often you test the water for legionella and the temperature of the system depends on the system in place and its components, and the outcome of the risk assessment. 

We will consider the issue of legionella and dental waterline management when we review the safe key question. This relates to Regulation 15: Premises and equipment.