Turning the Risk Assessment Into a Practical Control Programme
A Legionella risk assessment identifies the hazards within a water system.
A Written Scheme of Control sets out how those risks will actually be managed.
Source Water Compliance prepares practical, site-specific Written Schemes of Control for organisations responsible for hot and cold water systems.
The document brings together the control measures, monitoring requirements, responsibilities and corrective actions needed to manage Legionella risk on an ongoing basis.
HSE guidance states that once Legionella risks have been identified and assessed, an effective written control scheme should be prepared, implemented and properly managed.
What Is a Written Scheme of Control?
A Written Scheme of Control is the practical management document used to describe how Legionella risks will be controlled at a particular site.
It should be based on the findings of the Legionella risk assessment and reflect the actual water systems, occupancy and management arrangements present.
It should not simply be a generic document copied from one property to another.
HSE’s L8 gives Approved Code of Practice status to the control scheme, alongside risk assessment, the role of the responsible person and review of control measures.
A good Written Scheme should make it clear:
what needs to be done → who does it → how often → what the acceptable limits are → what happens when something goes wrong.
What We Include
The exact content will depend on the premises and systems identified during the risk assessment, but a Written Scheme may include:
Management Structure
Identification of:
- Dutyholder
- Responsible Person
- Deputy Responsible Person where appropriate
- Contractors and service providers
- Communication arrangements
- Individual responsibilities
Clear allocation of responsibilities is essential because control measures are only effective when everyone understands their role.
Water System Information
The scheme can describe:
- Incoming water supplies
- Cold water storage
- Booster systems
- Calorifiers
- Hot water circulation
- Point-of-use heaters
- TMVs
- Showers
- Water softeners
- Other relevant equipment
An up-to-date schematic drawing can also form part of the control documentation where appropriate.
Control Measures
The document sets out the measures used to minimise Legionella risk, such as:
- Temperature control
- Flushing of little-used outlets
- Shower cleaning and descaling
- Tank inspections
- TMV servicing
- Calorifier monitoring
- Water treatment where applicable
- Sampling where justified
- Cleaning and disinfection
- Management of vacant or low-use areas
Monitoring Frequencies
The Written Scheme should identify what needs to be checked and how often.
Depending on the system, this may include:
- Cold water temperatures
- Hot water temperatures
- Calorifier flow and return temperatures
- Sentinel outlets
- Representative outlets
- Cold water storage temperatures
- Little-used outlet flushing
- Showerhead cleaning
- TMV servicing
- Tank inspections
- Expansion vessel checks
- Water treatment parameters
- Microbiological sampling where applicable
The frequencies should reflect the system, findings of the risk assessment and relevant guidance rather than being selected arbitrarily.
Corrective Actions and Escalation
Monitoring is only useful if there is a clear response when results fall outside the required limits.
The Written Scheme should therefore explain what action should be taken when there is:
- A high cold water temperature
- Low hot water temperature
- Poor circulation
- Failed calorifier temperature
- Evidence of stagnation
- Unsatisfactory tank condition
- A failed TMV
- Missed monitoring
- An unusual sampling result
- Loss of system control
Corrective actions may include flushing, investigation, adjustment, maintenance, cleaning, sampling or escalation to the Responsible Person.
This makes the scheme a working management document rather than simply a compliance file.
Responsibilities Must Be Clear
One of the most common weaknesses in water hygiene management is uncertainty over responsibility.
This is particularly important within:
- Multi-tenant buildings
- FM-managed sites
- Landlord and tenant arrangements
- Large estates
- Healthcare premises
- Education estates
- Hotel portfolios
- Residential developments
A Written Scheme can clearly establish who is responsible for monitoring, maintenance, remedial actions and record keeping.
That clarity helps prevent important tasks being missed because each party assumes somebody else is dealing with them.
Site-Specific, Not Generic
A generic control document may look comprehensive but still fail to reflect how the building actually operates.
Our Written Schemes are developed around factors including:
- The specific water systems present
- Building occupancy
- Low-use areas
- Vulnerable populations
- System complexity
- Existing monitoring arrangements
- Access restrictions
- Responsibilities
- Previous risk assessment findings
The result is a document designed to be used by the people managing the site.
Written Schemes for Multi-Site Portfolios
For organisations responsible for several properties, consistency can be particularly useful.
Source Water Compliance can develop Written Schemes using a common structure across a portfolio while keeping the individual controls site-specific.
This can help facilities and compliance teams:
- Standardise monitoring
- Compare sites
- Train staff
- Review contractor performance
- Identify missing records
- Manage corrective actions
- Demonstrate a consistent management approach
Reviewing an Existing Written Scheme
A Written Scheme should not remain unchanged indefinitely.
A review may be appropriate following:
- A new Legionella risk assessment
- Changes to the water system
- Refurbishment
- Changes in occupancy
- New plant
- Changes in responsibility
- Repeated monitoring failures
- Significant sampling results
- Changes in control strategy
The scheme should continue to reflect the way the building and water systems are actually being managed.
Independent Review of Existing Documentation
If a Written Scheme already exists, Source Water Compliance can review it against:
- The current Legionella risk assessment
- The systems physically present
- Existing monitoring records
- Site responsibilities
- Current operational arrangements
- Applicable Legionella guidance
This can identify situations where the written procedures no longer match what is actually happening on site.
Working in Accordance With Legionella Guidance
Our Written Schemes of Control take account of applicable HSE guidance including:
HSE Approved Code of Practice L8 – Legionnaires’ disease
HSG274 – Legionnaires’ disease: Technical guidance
HSG274 describes written control schemes as part of the framework for managing Legionella risk and emphasises that the scheme should specify the control measures and how those measures are to be carried out.
Recent HSE enforcement notices also show that failure to devise and implement a suitable Written Scheme remains an active compliance issue.
Supporting Services
A Written Scheme is often most effective when it sits alongside:
Legionella Risk Assessments
To identify the risks and determine the required control measures.
Water Hygiene Monitoring
To implement the routine checks required by the scheme.
Water Hygiene Audits
To verify that the controls described are actually being completed.
Water Hygiene Maintenance & Servicing
To support tasks such as TMV servicing, shower cleaning and other planned maintenance.
Water Sampling & Microbiological Testing
Where sampling forms part of the site’s control or investigation strategy.
Water System Schematic Drawings
To clearly show the principal water systems covered by the scheme.
Arrange a Written Scheme of Control
If your organisation needs a new Written Scheme of Control, or your existing document no longer reflects the current water systems or management arrangements, Source Water Compliance can help.
We can develop a clear, practical document based on the site, risk assessment and existing control measures.