Legionella Risk London: Lessons learnt at famous apartments

by Peter Gunn, on 04-08-2021
Find me on:


Legionella Risk London: Lessons learnt at famous apartments

On the 20th March 2019 the London Evening Standard reported that Public Health England had confirmed a case of Legionnaires’ disease within the Dolphin Square complex of private flats in Pimlico, Westminster near the River Thames in London.


The flats were built in the 1930’s and at one time was the most developed garden square of private housing in London. The 10-storey development of over 1200 flats has been described as one of London’s most notable apartment blocks and has had a number of both famous and notorious residents in its time.


New call-to-action


Positive Legionella samples at Dolphin Square

Initial water samples taken from the flexible shower hose and bathroom sink of the affected resident’s flat tested positive for Legionella. Subsequent information taken from the apartment block’s own website indicated there were a total of three confirmed Legionnaires’ disease cases within Nelson, Beatty and Hawkins Houses. The third and final case was confirmed by Public Health England on 1st July 2019, shortly after the London Evening Standard reported this as a Legionella outbreak.


Although there was existing routine monitoring and legionella sampling in place prior to the cases undertaken by the appointed water systems contractor in association with the Dolphin Square management company, a logical conclusion to draw is that the regime may not have been adequate. The post incident investigation also involving the Health and Safety Executive [HSE], Westminster City Council and Public Health England [PHE] led to a multi-faceted programme of inspection, sampling, outlet flushing and de-scaling, systemwide chlorination of the hot water systems and significant riser and other pipework replacement and other remedial actions.


The Legionella sampling programme alone was reported to include 3 flats per floor in each house on a weekly basis initially and which led to multiple further remedial actions. A programme was also undertaken to significantly increase occupant awareness of the factors which can increase water hygiene and Legionella risks. A Dolphin Square Water Safety Group was also subsequently convened to meet monthly to oversee the critical aspects of Legionella and other waterborne pathogen risk management.


What lessons can be learnt from the Dolphin Square Legionella outbreak and could this have been avoided?

Published information from the press, Dolphin Square Ltd themselves and other sources provide some indicators as to why these cases may have occurred, though it is unlikely there was a ‘smoking gun’, causal to the outbreak.


Legionellosis risks from hot and cold water systems in most residential settings are generally considered to be low owing to regular water usage and turnover. It is also true to say that not all systems require elaborate control measures and simple, proportionate and practical actions are often all that is required to minimise Legionella risks for residential occupants of any age or vulnerability.


The flip side of these statements in a residential setting, may be that many occupants remain either completely unaware or indifferent to Legionellosis risks as they go about their day to day lives. Public Health England’s monthly surveillance reports for Legionnaires' disease frequently also show a majority of Legionnaires’ disease cases derived from community settings and that it is possible or even likely that some of these cases come from domestic properties.


So, both landlords and residents [tenants] have a role to play in risk minimisation and we have set out the background responsibilities and the type of simple practical tasks that can and should be undertaken routinely.


HSE guidance acknowledges that in many residential settings landlords have a legal responsibility to ensure the health and safety of their tenants by keeping properties safe and free from health hazards. The HSE provide very clear advice on Legionella and landlords responsibilities


What are landlords responsibilities to manage legionella?

The HSE provide advice on their website in respect to Legionella and landlords’ responsibilities. In a nutshell, all systems require a Legionella risk assessment in the first instance. The situation was clarified following the publication in 2013 of the fourth edition of the Health and Safety Executive’s Approved Code of Practice [ACoP]: ‘Legionnaires’ disease, The Control of Legionella Bacteria in Water Systems’, L8. Although ACoP L8 was updated, it didn’t change or alter the responsibilities placed on landlords who have always had a duty to carry out Legionella risk assessments and manage the risk from Legionella bacteria to their tenants.


Legionella Risk Assessment

The information on the HSE’s website states:

“The practical and proportionate application of health and safety law to landlords of domestic rental properties is that whilst there is a duty to assess the risk from exposure to Legionella to ensure the safety of their tenants, this does not require an in-depth, detailed assessment”.


All systems should be assessed but the programme of assessment should be reasonably practicable. This may mean, in the first instance, undertaking a desktop appraisal of risk to identify properties that could represent an increased Legionella risk, for example:

  • Properties in which the typical occupants may be of increased susceptibility to infections (e.g., sheltered housing schemes or hostels);

  • Larger and more complex properties and water systems (e.g., multi-dwelling units, etc.);

  • Features of the water system design that increase the likelihood of bacterial colonisation (e.g., the presence of hot or cold water storage tanks);

  • The age of construction and/or subsequent refurbishments: this may indicate properties in which plumbing is unlikely to comply with current standards.

Of course, there may be other reasons why one property represents a higher risk than another and there is no substitute for an inspection of site water services when it comes to determining the actual risk. A Legionella risk assessment of a sample of sites/buildings can provide a representative cross-section of the properties to identify the priorities for the future programme of assessments and control measures.

Legionella Control Measures

The HSE’s ACoP L8 states that:

“All systems require a risk assessment, however not all systems will require elaborate control measures. A simple risk assessment may show that the risks are low and being properly managed to comply with the law. In such cases, you may not need to take further action, but it is important to review your assessment regularly in case of any changes in your system, and specifically if there is reason to suspect it is no longer valid”.

And “Other simple control measures to help control the risk of exposure to Legionella include:

  • Flushing out the system prior to letting the property;

  • Avoiding debris getting into the system (e.g., ensure the cold water tanks, where fitted, have a tight fitting lid);

  • Setting control parameters (e.g., setting the temperature of the hot water cylinder (calorifier) to ensure water is stored at 60°C);

  • Make sure any redundant pipework identified is removed;

  • The risk is further lowered where instantaneous water heaters (for example combi boilers and electric showers) are installed because there is no water storage.”

Persons undertaking the control measures and any other work on the plumbing systems should receive adequate Legionella training in the risks from waterborne bacteria and competent to undertake the work.

Legionella: What residents (or tenants) need to know!

The HSE state:

“Tenants should be advised of any control measures put in place that should be maintained e.g. not to adjust the temperature setting of the calorifier, to regularly clean showerheads and tenants should inform the landlord if the hot water is not heating properly or there are any other problems with the system so that appropriate action can be taken".

“Where showers are installed, these have the means of creating and dispersing water droplets (aerosols) which may be inhaled causing a foreseeable risk of exposure to Legionella. If used regularly (as in the majority of most domestic settings) the risks are reduced, but in any case, tenants should be advised to regularly clean and disinfect showerheads. Additionally, ‘Report faults with the system so that appropriate action can be taken".

Additional actions for properties left vacant

The management of void properties and their re-occupation process will also have an impact on the risk to residents. Again, the HSE’s advice remains:

“It is important that water is not allowed to stagnate within the water system and so there should be careful management of properties left vacant for extended periods (e.g., student accommodation left empty over the summer vacation). As a general principle, outlets on hot and cold water systems should be used at least once a week to maintain a degree of water flow and minimise the chances of stagnation. To manage Legionella risks during non-occupancy, consideration should be given to implementing a suitable flushing regime or other measures such as draining the system if it is to remain vacant for long periods”.



All rental properties require a Legionella risk assessment and landlords or agents with responsibility for a large number of properties require a robust plan for the management of the risk from Legionnaires’ disease.


Whilst landlords may not have a mandatory obligation under law to provide residents with information relating to risks associated with domestic water systems, the HSE are clear in their view and advise that:

“landlords should inform their tenants about the action taken to control the risk from Legionella bacteria and advise them how they should be maintained”.


Not only that:

"the HSE and Local authorities do not proactively inspect premises or even ask for evidence that landlords have undertaken risk assessment, however if a tenant were to contract Legionnaires’ disease, the landlord may well be liable to prosecution under the Health and Safety at Work etc. Act and would have to demonstrate to a court they had fulfilled their legal duty”.


If you have questions regarding the issues raised above or you would like to speak with one of our consultants, please click here to get in touch.

Editor’s Note: The information provided in this blog is correct at date of original publication – August 2021.

© Water Hygiene Centre 2021


New Call-to-action

About the author

Peter Gunn

Peter has been acting as an AE [water] and providing competent help services to multiple public sector and public services client in both the Midlands and North of England since 2004, and working within Legionellosis risk management since 1997. Peter currently acts as AE [water] for 11 large public services client’s including University’s, Councils, Healthcare and Constabularies.

Share your thoughts