As Britain prepares to sizzle with temperatures expected to reach 37°C in some areas over the next four days, water experts are warning that a potentially deadly disease can thrive in hot tubs, pools and other domestic water devices.
The risk of Legionnaires’ disease - a potentially fatal lung infection caused by inhaling droplets of water containing Legionella bacteria – increases during hot weather, particularly in stagnant or untreated water systems.
According to new research launched today (One Poll survey of 2000 UK consumers, May 2026), one in ten Brits now own a hot tub or jacuzzi – meaning there are almost 3 million now in operation across the country. A further one in ten (13%) have a swimming pool or cold plunge bath.
Yet despite their growing popularity, maintenance standards appear to be falling short. More than half (54%) of owners say they are not fully confident that their cleaning and maintenance routines are robust enough. Among those, 28% admit they have not considered or would rather not think about hygiene risks and associated germs.
More worrying still, only 24% follow a set cleaning schedule - while a staggering 92% do not regularly test for Legionella, despite the potentially serious health consequences.
Staying safe
With this, Hydrohawk, the UK’s leading Legionella authority, has provided crucial advice on how to stay safe as households enjoy the rising temperatures.
Greg Rankin, CEO at Hydrohawk, comments: “As temperatures rise, it’s easy to get caught up in the excitement of barbecues and evenings outdoors. However, behind the scenes, Legionella remains a silent yet serious threat - especially in warm, stagnant water systems, such as unused hot tubs or spa pools.
“As climate change continues to create ideal conditions for Legionella bacterium to thrive, raising awareness and taking preventative steps has never been more critical.”
It is estimated (Britsafe) that there are 4,000-6,000 cases of Legionnaires’ disease in the UK each year, killing between 7-12 percent of all those infected. As the UK experiences warmer average temperatures and more frequent weather extremes due to climate change, this risk is increasing.
Temperature range
Hot tubs operate in the same temperature range that supports Legionella growth (roughly 25-45°C). That, and the scope for water spray, can increase the risk of Legionella if not properly managed.
Intermittent use – particularly during fluctuating hot and wet spells like recently experienced in the UK - remains a particularly critical safety concern. This is because when a hot tub sits unused, water often stagnates in the plumbing and fittings, disinfectant levels fall away and biofilm can build up on pipes, jets, and filters, creating the perfect conditions for Legionella bacteria to thrive. When reusing for the first time in a while, it is therefore vital to ensure a thorough clean, drain and disinfection of the entire system before anyone gets in.
Greg Rankin, CEO at Hydrosense, comments: “Hot tubs, in particular ,have grown significantly in popularity over recent years, so it’s vital that homeowners understand how to operate them safely, especially as they can provide ideal conditions for Legionella growth.
“When left unused for any length of time, the risk of Legionella infection increases significantly. Fortunately, there are some simple steps people can take to minimise that risk.
Simple steps
“Always ensure your hot tub has been treated with the correct chemicals at the appropriate levels before switching it on. Chlorine and bromine are the most commonly used disinfectants and can help keep the risk to a minimum.
“As part of this, a quick and easy Legionella test can help to detect potential risks early, so that you’re sure that water-borne illnesses won’t get in the way of your summer fun.”
For further information please visit: www.hydrohawk.co.uk
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