Dozens of water samples failed hygiene checks last year, with some results leading to spa pools being closed and an airport water tanker being withdrawn from service.
New first-party data from Acorn Environment Services shows that 48 water samples failed during 2025.
The water hygiene company took more than 1,800 samples and completed 3,132 jobs across the UK, ranging from Stromness in Orkney to the Isle of Wight.
Acorn also identified more than 1,500 non-compliance issues at client properties during routine inspections and monitoring.
The figures do not represent confirmed cases of illness or mean that every affected property was unsafe. However, they show how routine checks can uncover problems that may otherwise remain hidden inside tanks, pipework and other water systems.
Failed checks forced pools to close
Some of the failed samples were linked to spa pools where testing identified high readings of Pseudomonas or total viable count bacteria.
The affected pools were taken out of use before being drained, cleaned and superchlorinated. Their surfaces, filters and strainers were also treated before further samples were taken and the pools were cleared to reopen.
Acorn also conducted monthly checks on water loaded onto aircraft at a local airport.
Following recent sample failures, the affected water tanker was immediately removed from operation. It was drained and superchlorinated before being retested and returned to service.
A failed sample does not necessarily mean somebody has become ill. Depending on the type and result, however, it may require facilities or equipment to be taken out of use while corrective work is completed.
More than 1,500 problems identified during routine visits
Acorn recorded more than 1,500 non-compliance issues across its water hygiene work during 2025.
Clients were notified of each issue through service reports and the company’s online portal. The issues remained open until the required corrective action had been completed and signed off by an Acorn operative.
The company also completed 252 Legionella risk assessments and written schemes of control. These are used to identify potential risks and establish the measures required to manage them.
Cold water storage tanks at 48 properties were cleaned and disinfected after sediment or sludge was found during six-monthly inspections.
Water systems at a further 15 new-build properties in Lancashire and Yorkshire were disinfected as part of their handover to local authorities.
Stockport accounted for two-thirds of Acorn’s recorded work
Stockport was the busiest location within Acorn’s 2025 operational records, accounting for 2,105 jobs, or 67.2% of the company’s total workload.
Manchester ranked second with 248 jobs, followed by Leeds, Birmingham and Sheffield.
Location Jobs completed Share of all jobs
Stockport 2,105 67.2%
Manchester 248 7.9%
Leeds 55 1.8%
Birmingham 52 1.7%
Sheffield 48 1.5%
The figures reflect Acorn’s customer base and existing contracts. They should not be interpreted as a ranking of water quality, unsafe buildings or cases of Legionnaires’ disease.
Hidden water hygiene problems may go unnoticed
John Whiteley-Wilkson, Managing Director of Acorn Environment Services, said:
“Water hygiene problems can be difficult to spot because many of the warning signs are hidden inside tanks, pipework and systems that people rarely see.
“Our records show that routine monitoring identified more than 1,500 compliance issues in one year.
Some of the failed samples required pools or equipment to be taken out of operation until corrective work had been completed and further testing confirmed they could safely return to use.
“A failed sample does not automatically mean somebody has become ill, and these results should not be confused with confirmed cases of Legionnaires’ disease.
“They do demonstrate why regular checks matter. Potential problems can be identified and addressed before the affected system is allowed to continue operating as normal.
“Those responsible for buildings and water systems should ensure risks are assessed, suitable controls and records are maintained, and identified faults are addressed rather than left unresolved.”
The latest UK Health Security Agency figures recorded 472 cases of legionellosis in England and Wales during 2024, including 463 confirmed cases of Legionnaires’ disease.
These national figures are separate from Acorn’s operational, sampling and compliance data.
