Most problems are best handled before they even happen. As in life, so in business, great managers run their businesses successfully by predicting problems and solving them before they appear. Better said, knowing what might happen, they take precautions that won’t lead to a problem.
When talking about water safety, precaution is everything. A building may look safe on paper, but water systems can quietly carry risk long before a single user steps inside. This is why owners should carry out pre-installation risk assessments that will address future hazards. One of the worst bacteria that may cause health problems is Legionella, which is why this risk assessment is among the essential ones.
Ensure Legionella Safety
from the Start
Waiting until a system is operational before addressing legionella risk is no longer considered best practice. Once hot and cold water services are installed, significant changes become costly and disruptive, particularly in healthcare premises and domestic hot environments where vulnerable users are present.
A proactive assessment reviews water flow, storage conditions and maintenance access while plans are still fluid. Systems designed with control in mind are easier to monitor, clean and manage on a regular basis. Even simple control measures, such as allowing space for tight fitting lids on cold water tanks or ensuring hot water reaches safe temperatures, can make all the difference.
What is a Pre-Installation Legionella Risk Assessment?
A pre-installation legionella risk assessment is a structured review of proposed hot water and cold water systems before construction begins. It assesses whether the design unintentionally creates conditions where legionella bacteria could multiply and pose a potentially fatal form of exposure to building users.
This type of risk assessment examines planned pipe runs, stored water volumes and areas where water may stagnate due to poor circulation. Rather than waiting for faults to be discovered during commissioning, it highlights issues when changes can still be made easily. It gives responsible persons confidence that the system is engineered with long-term safety in mind.
The assessment considers key design aspects including:
Pipework configuration and materials
Hot and cold water storage and circulation systems
Temperature control measures
Accessibility for cleaning, maintenance, and sampling
Points of use and potential dead legs
System schematics and operational plans
Why Conduct a Pre-Installation Legionella Risk Assessment?
Legionnaires’ disease is not a historical hazard — it’s still very much present in today’s buildings. All it takes is warm, stagnant water
and a neglected system for legionella bacteria to multiply. The Health and Safety Executive is clear on one point: control is not optional.
It must begin before the first pipe is fitted and continue throughout operation.
A pre-installation legionella risk assessment gives you that control. Instead of discovering redundant pipework, oversized cold water tanks
or struggling hot water systems after installation, risks are addressed before they turn into costly mistakes.
Early planning prevents exposure to substances hazardous to health and keeps your water services ready for ongoing monitoring.
It’s not just compliance — it’s protection for people, property and reputation.
Carrying out the assessment before installation offers multiple advantages
Prevents Legionella risks from being built into your system design
Ensures compliance with ACoP L8, HSG274 and BS 8580-1 standards
Avoids costly retrofits and design alterations post-installation
Improves long-term safety and system efficiency
Supports duty holders and responsible persons in meeting legal obligations
When it comes to legionella control, planning ahead is far more effective than reacting after installation. A pre-installation assessment does not delay a project; it protects it. It gives designers and contractors peace of mind that their system will meet regulatory standards from day one.
More importantly, it ensures building users are never placed at unnecessary risk. By embedding best practice before pipework is even laid, future operation becomes easier, safer and more cost-efficient. Choosing to assess early is not just compliant — it is responsible.
Who Needs a Pre-Installation Assessment?
Any organisation commissioning or modifying hot and cold water systems should consider a pre-installation assessment, particularly when working in environments where health is a primary concern. Healthcare premises, care homes, schools, leisure centres and large domestic hot properties face higher risk due to regular water usage and increased exposure to small droplets. Building projects involving cold water storage tanks, complex distribution layouts or significant changes to existing pipework require assurance that control measures are in place. Duty holders may feel competent in general management but legionella control is a specialist area where professional guidance prevents costly mistakes.
This service is essential for:
New builds and refurbishments involving hot and cold water systems
Healthcare facilities, care homes, and dental practices
Commercial buildings, offices, and hotels
Industrial sites with complex process water systems
Housing developments and large residential projects
Responsibility for water safety cannot be assumed; it must be proven. A pre-installation legionella risk assessment demonstrates active compliance rather than passive intent. Whether overseeing a refurbishment or designing from scratch, ensuring that systems are built to maintain safe temperatures and avoid stagnation should be seen as essential rather than optional. Those who take risk seriously act before installation, not after.
What Our Customers Say
“The team at Comfort Services Group were awesome when they carried out the Legionella Control works at our offices, they were very accommodating, Tom and the guys on site were a pleasure to work with. I would recommend the services of Comfort Services Group without reservation. Excellent First impressions with the Office Team, which was mirrored by the guys who did the work. Thanks guys.”
Michael Green
“I have had Comfort commissioning working on different projects for the companies i have worked for over the past 15 years. They have assisted in many difficult projects throughout the country. Andy and Lawrence have been very professional and helpful. i found their attitude, and pro-active approach to be of very high standard. i will always push to use them on future projects”
Chris Richards
“Comfort commissioning are a great company, they deliver great services and the team there are very helpful and efficient. They really do care about their customers and take a keen interest in ensuring a high level of customer service is maintained at all times.”
Gary Clatworthy
“Fantastic service from Comfort from start to finish. Very responsive, friendly, reliable and professional.”
Sarah
“Contacted Comfort Commissioning Services Ltd for advice about unusual deposits in the header tank of an open vented domestic heating system. Not core business for them, but one of their directors responded to me really quickly via email with some excellent free advice which was greatly appreciated. Very impressed.”
Pete Davies
Our 5-Step
Pre-Installation Legionella Assessment Process
01
Design Review
Every assessment begins with a detailed analysis of your proposed water system layout. Pipe work configurations, temperature controls, flow rates and access points are reviewed to identify where cold water could become warm, or hot water may fail to reach pasteurisation thresholds. Factors such as stored water volumes, insulation, valve positioning and vent locations are examined with future maintenance in mind. By evaluating plans at this level, potential issues are caught early and changes can be implemented before installation work begins, saving both time and expense. A well-planned system is far easier to manage and far safer in operation.
02
Risk Identification
Once the design is understood, attention turns to spotting conditions where legionella bacteria may gain a foothold. Areas where water temperatures may fall into the favourable range for growth are highlighted along with any sections that could suffer from low usage or prolonged stagnation. Redundant pipework, oversized tanks and dead legs are flagged as potential concerns. The goal is not to criticise but to reveal real risks before they become problematic. Even minor design flaws can lead to major safety issues once systems are operational, so clarity at this stage is vital for responsible water management.
03
Recommendations
Following risk identification, clear recommendations are provided to strengthen control measures. Suggestions may include adjusting pipe gradients to improve drainage, resizing cold water storage to reduce dwell time or ensuring access hatches are large enough for future inspections. Where hot water generation appears insufficient, alternative heaters or circulation improvements may be proposed. Each recommendation is designed to minimise exposure opportunities while maintaining practical installation requirements. Rather than generic advice, guidance is tailored to your property type, usage pattern and regulatory expectations. The outcome is a system aligned with both safety and usability.
04
Compliance Guidance
Meeting legal requirements is not just about avoiding enforcement; it protects lives. Compliance guidance explains how your proposed installation aligns with the Health and Safety Executive’s approved code of practice and other relevant regulatory standards. Where improvements are needed to satisfy safety legislation, they are presented in clear terms without unnecessary jargon. This ensures all stakeholders, from contractors to duty holders, understand their obligations. Compliance becomes easier when expectations are made visible and achievable. Knowing that your system has been assessed against recognised best practice provides confidence before commissioning even begins.
05
Final Report
Every assessment concludes with a structured report summarising all findings, risks identified and action points. This document serves as both evidence of due diligence and a practical roadmap for installation teams. It outlines where control measures should be integrated and highlights areas requiring ongoing monitoring once the system is in use. Rather than being filed away, it becomes a working tool used throughout construction and operation. The report gives clarity, accountability and a clear reference point should inspections be carried out by the safety executive or other authorities at a later date.
Book Your Pre-Installation Legionella Risk Assessment
It doesn’t matter if you’re trying to keep your home shower heads regularly clean or you’re looking for business solutions that will handle entire buildings; we’re here to handle this problem for you before it even happens. Ask for an example of our work and ensure we’re the best there is.
Give us a call and let us find those potentially weak spots that might cause a severe problem later on. Handle this issue before the installation is completed, which is the best stage to conduct a risk assessment. With Comfort Services Group, you can be comfortable knowing you’re in the right hands.
Get a FREE consultation
We will process your data in accordance with our Privacy Policy.
You can opt out of these communications at any time by updating your preferences.
Frequently Asked Questions
When should a Pre-Installation Legionella Risk Assessment be carried out?
A pre-installation legionella risk assessment should be carried out during the design or planning stage of any new water system or major refurbishment. It is most effective before equipment is installed, as changes to pipework or cold water storage are far easier to implement at this stage than after commissioning. Acting early prevents costly redesigns and ensures compliance with health and safety requirements. Delaying assessment until handover introduces unnecessary risk to building users.
Who is responsible for arranging a Pre-Installation Legionella Risk Assessment?
Responsibility usually falls to the duty holder or building owner, but designers, contractors and project managers also have obligations under health and safety law. Anyone controlling premises where water systems are being installed must ensure risks are identified and managed. While individual roles vary depending on contracts, accountability cannot be ignored or passed on. Appointing a competent assessor early in the process demonstrates responsible management and protects all parties from future liability.
How does a Pre-Installation assessment differ from a standard Legionella Risk Assessment?
A pre-installation assessment evaluates the system before it exists physically, focusing on design choices and proposed layouts. A standard legionella risk assessment is performed once the system is operational and looks at real-world conditions such as water temperatures and usage patterns. By intervening at the design stage, pre-installation assessments prevent risks from being built in. They are proactive rather than reactive, making long-term management far easier and more cost-effective.
Can you assist with follow-up assessments after installation?
Yes. While pre-installation assessments control risk at the design stage, ongoing monitoring remains essential once the system is live. Follow-up assessments confirm that installation matches original plans and that temperatures, flow rates and control measures remain effective. Post-installation reviews also highlight any changes in usage that may influence safety, such as redundant outlets or new building occupants. Maintaining compliance is a continuous process, not a one-off action.
Why is conducting a risk assessment during the design stage of a water system important?
Assessing water system safety during design prevents flaws from becoming permanent. Once pipework and cold water tanks are installed, modifications become disruptive and expensive. Early assessment ensures water flow is maintained, temperatures remain outside the bacterial growth range and future maintenance is achievable. It is far easier to prevent stagnation or dead legs than to fix them after construction. By eliminating hazards before installation, projects stay on schedule and users stay protected.
How do pre-installation assessments help meet health and safety regulations for Legionnaires’ disease prevention?
Health and safety regulations require duty holders to identify and control risks associated with legionella bacteria. Pre-installation assessments demonstrate compliance before occupation, showing regulators that risks were considered from the outset. They provide evidence of due diligence and ensure systems are designed with access for cleaning, monitoring and testing. Rather than relying on corrective action after commissioning, early assessment embeds safety into the system’s DNA, making long-term compliance easier to maintain.
