In August, New York City finally declared the end of a deadly Legionnaires’ disease outbreak in Central Harlem.
The numbers were stark: 114 confirmed cases, around 90 hospitalisations and seven deaths, with the outbreak traced to cooling towers on Harlem Hospital and a nearby city-run site (AP News).
Investigators ultimately found 12 cooling towers testing positive for Legionella across the neighbourhood, many on residential or mixed-use buildings (People.com).
As a cooling systems company heavily involved in both the maintenance and refurbishment of cooling towers for residential properties in London, we should look at Harlem and see a very clear warning sign for UK landlords, housing providers and managing agents – especially where cooling towers sit above people’s homes.
Harlem: when cooling tower maintenance goes wrong
New York actually has some of the toughest cooling-tower rules in the world. Since the South Bronx outbreak in 2015, Local Law 77 has required owners to register every cooling tower, have a written Maintenance Program and Plan, test for Legionella and file an annual certification (NYC Cooling Tower Guidance), something which is mirrored in the UK.
Despite this, Harlem’s outbreak appears to have been driven by basic failures in cleaning and inspection:
- State law currently requires Legionella testing at least every 90 days during the operating season (NYC Cooling Tower Testing Rules)
- Cooling towers at Harlem Hospital allegedly filled with untreated stormwater after heavy July rain – a perfect environment for Legionella – and several city-owned towers had a history of violations (NY Post Report)
- Non-compliance with NYC’s cooling-tower rules can attract fines of roughly $500–$2,000 per violation per day, plus enforcement action and potential tower shutdown (TowerWater Compliance Guide)
After Harlem, the city is now proposing to tighten the regime even further – pushing for monthly Legionella testing during the operating season and higher penalties for non-compliance (NY Post – Proposed Stricter Rules).
If a city with that level of regulation can still see 100+ cases from cooling towers, what does that mean for major residential buildings in London?
The UK Picture: Cooling Tower Legionella Risk Above Residential Homes
In the UK, we already know that poorly-managed water systems can displace residents. A recent HSE prosecution against Sanctuary Housing followed extensive Legionella contamination at a sheltered housing scheme in Birkenhead. All 44 water samples came back positive, residents had to be evacuated, and the landlord was fined £900,000 plus costs under the Health and Safety at Work etc. Act 1974 (Inside Housing).
Legionella Control Framework: HSE ACOP L8 and HSG274 Duties
- Health and Safety at Work etc. Act 1974 and COSHH Regulations 2002 – duty to assess and control exposure to harmful substances, including Legionella.
- HSE ACOP L8 and technical guidance HSG274 – require a suitable and sufficient Legionella risk assessment, a written scheme of control, a named responsible person, and appropriate monitoring/record-keeping
- Notification of Cooling Towers and Evaporative Condensers Regulations 1992 – requires notification to the local authority.
For residential landlords specifically, HSE is clear: there is a legal duty to assess and control Legionella risk for tenants, even in domestic settings (HSE Landlord Legionella Duties).
Guidance from UK bodies shows a strong trend toward reviewing the risk assessment at least every two years, or sooner if system changes occur or evidence shows controls are failing (NRLA Legionella Guidance).
For a London high-rise with a cooling tower serving apartments, that means:
- A current risk assessment (not older than ~2 years).
- A detailed written scheme: diagrams, control measures, sampling plan, emergency response.
- Evidence of routine tasks in line with HSG274.
What EHOs will expect– the mechanical focus
Environmental Health Officers in the UK are increasingly aware that Legionella risk often originates from plant condition and access failures, not just dosing levels.
Here’s what they now typically look for:
1. A current Legionella risk assessment (mechanical detail included)
Including:
- Condition of pumps, fans, pipework and structure
- Evidence of full-flow circulation
- Removal of dead legs
- Verification of drift eliminator integrity
Reference: Risk Assessment Law
2. A mechanical-focused written scheme of control (6–12 month plan)
This must show planned engineering works, not just sampling:
- Pump servicing and condition monitoring
- Annual cooling tower mechanical strip-out
- Fan and gearbox checks
- Structural inspections
- Access improvements (handrails, walkways, ladders, anchor points)
- Hatches and lighting upgrades
Reference: HSG274
3. Records & logbooks that include mechanical data
- Monitoring sheets
- Repairs and replacements
- Access inspections
- Remedial Actions
- Photographic evidence of deterioration
4. Emergency & Rehousing Plan
- Action steps if contamination is detected
- Criteria for decanting residents
- Example case: £900k Sanctuary fine
Where serious deficiencies exist, EHOs or HSE can issue Improvement or Prohibition Notices. Penalties for Legionella mismanagement include unlimited fines and potential imprisonment (UK Legionella Regulations Guide).
Why this matters for London
Many London blocks have inherited plant from the 80s–2000s – cooling towers on roofs originally designed for commercial buildings that now serve newly converted residential spaces.
In these buildings, Legionella responsibility can easily fall between:
- The freeholder
- The managing agent
- The FM contractor
- The water-treatment specialist
Harlem is the reminder that “we thought someone else was doing it” isn’t a defence.
The Harlem case and the £900k Sanctuary fine are clear evidence: passive compliance is no longer enough. For London’s residential blocks, comprehensive, mechanically-focused cooling tower maintenance should be a key priority in the defence against catastrophic Legionnaires’ outbreaks and unlimited regulatory fines under UK law. The responsibility rests squarely with Duty Holders to move beyond basic testing and fully stress-test their written schemes of control.
Harlem shows that even the strictest regulations can be undone by basic lapses in maintenance and oversight. Review your compliance today to protect residents and mitigate your risk.