Legionella Risk in Hot Tubs

Temperature Instrumentation

Sarah Cuthbert
8 Sept 2022

With a rise in staycations post lockdown and COVID-19, people have been enjoying more time at home rather than jetting off to exotic destinations. The UK public has been investing in luxuries such as hot tubs and home spas to help themselves relax and unwind all year round. Total sales of hot tubs in the UK have increased by 20% for home, leisure and rental properties. Although hot tubs help you relax and unwind, they also come with a high level of maintenance to ensure they are safe for those who use them. One of the most significant health risks of hot tubs and spa pools is the presence of legionella bacteria in the water. Whether you are an owner, in control, or responsible for a hot tub, our blog will tell you about the risk of legionella in hot tubs and spa pools and how you can ensure you can enjoy yours safely and risk-free.

Hot Tub Bacteria Risks

Hot tubs are the perfect breeding environment for harmful bacteria such as E .coli, Pseudomonas, Coliforms, Legionella and other waterborne pathogens. As they are a much smaller area than swimming pools, hot tubs have a higher concentration of people than water and, subsequently, a higher number of organic materials and bacteria from users’ bodies in the water. As well as the increased ratio of humans to water, the higher temperatures of hot tubs (typically 30 – 35C) amplify the risk as it is the perfect temperature for bacteria to spread rapidly. Hot tubs also have water jets that project water around and can cause a release of water vapours and aerosols through the bubbling of the water that can splash onto people and the nearby area or float on the surface of the hot tub. This can even be a risk for those not using the hot tub and could be near or touch it. The bacteria in water vapour then becomes an aerosol and can be breathed in by all in the hot tub environment, infecting all with the bacteria found in the water. All these factors make hot tubs highly likely to cause an outbreak of harmful bacteria to those in contact with the hot tub.

The water temperature, movement and aerosol creation make hot tub’s the perfect breeding ground for legionella. Legionella bacteria multiply rapidly in water between temperatures of 20 to 45 degrees Celsius, right between the average temperature of hot tubs. Legionella also breeds a supply of nutrients such as algae and scale, sludge or algae, all commonly found in unhygienic hot tubs. Previous outbreaks of legionnaires disease have been traced back to hot tubs from leisure centres, hotels, holiday homes and cruise ships.

Legionella is dangerous to humans as it causes legionnaires’ disease, also known as Pontiac fever or Legionellosis. It is a pneumonia infection caused by legionella bacteria in water. It can be found in natural water, but it particularly likes to grow in warm water environments. The disease attacks and infects the lungs after human inhalation through water droplets, such as water vapour and aerosols released in hot tubs. More can be read about Legionnaires Disease in our dedicated application note.

What are my Responsibilities?

Anyone who operates a hot tub/spa pool in the UK has a legal right to ensure that the water used is safe, does not put others at risk, and is under health and safety law. This includes those who design, manufacture and install the hot tub and pool system. The UK Health and Safety Executive has an Approved Code of Practice ACOP L8 - Management of Spa Pools: Controlling the Risks of Infection that provides advice on safely managing and controlling these risks. One of the essential methods is testing and monitoring water quality.

Although owners do not have any legal requirements for testing, it is within their best interest to regularly test for legionella and other bacteria. Regular testing helps owners protect themselves and other users from risk when using their hot tub. Regular testing should be carried out consistently and thoroughly to ensure your risk to bacteria remains low. It should be seen as essential to a maintenance routine when owning a hot tub.

Testing

Frontline Safety recommends the ETI Legionnaires’ Thermometer Kit for testing for legionella in hot tubs and pool spas. The kit contains everything you need to test, record and care for your testing equipment. This is an ideal piece of equipment for frequent testing at home, rental properties and holiday accommodations.

Owning a thermometer testing kit allows you to test your hot tub or spa pool frequently and consistently. Sending away legionella testing results can take as long as two weeks to receive the result. As Legionella bacteria can multiply rapidly, it is likely to double in population within only 24 hours. Leaving this time between testing and results is too risky if people were to chance using the hot tub in the meantime and risk infection. Using a thermometer testing kit can help prevent risk developing to this stage as users can regularly check the water system temperature and make suitable changes to the storage method, maintenance and temperature before bacteria grow. Following this method helps to prevent the growth of legionella, which is better than having to deal with the consequences.