Discovering a positive Legionella result in your water system can be an unsettling experience. Whether you’re a landlord, facility manager, or responsible person, knowing how to respond swiftly and responsibly is crucial to protecting health, maintaining compliance, and avoiding disruption.
We specialise in Legionella management, risk mitigation, and water system remediation. This guide outlines what a positive test result means, the immediate actions to take, and how a trusted Legionella contractor like us can support you throughout the process.
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Understanding a Positive Legionella Result
A positive Legionella result means that Legionella bacteria have been detected in your water system. These are typically measured in colony-forming units per litre (CFU/L). The higher the count, the more urgent the need for corrective action.
While it’s not always cause for alarm, it is a signal that your system may pose a risk—particularly to vulnerable individuals such as older adults, smokers, or those with weakened immune systems. Prompt intervention is essential to reduce the potential for Legionnaires’ disease, a serious respiratory condition caused by inhaling contaminated water droplets.
Step-by-Step: What to Do Next
While a positive result can be stressful, maintaining a clear head allows for efficient, effective decision-making. The key is structured, informed action.
Understand the concentration and location of the Legionella found. If the level is below 1000 CFU/L, repeat sampling may be sufficient. Higher levels typically demand more urgent and intensive intervention, including disinfection.
Make sure all relevant parties are informed, including building management, health and safety representatives, and, if appropriate, occupants or tenants. Early, transparent communication fosters trust and allows for coordinated action.
Depending on the risk, you may need to isolate certain outlets, restrict water use in affected areas, or install temporary point-of-use filters to protect occupants while further steps are taken.
Engage a water hygiene professional, who can conduct an expert assessment, guide remedial work, and ensure you’re aligned with legal obligations under the Health and Safety at Work Act, COSHH, and ACOP L8.
How We Help Manage Positive Legionella Results
Working with a dedicated Legionella contractor gives you access to specialist knowledge, reliable remedial services, and long-term peace of mind. Here’s what our support includes:
We examine your entire water system, mapping areas of concern such as dead legs, low-use outlets, and poor temperature control, and assessing your current water management plan.
Whether through thermal or chemical disinfection, our technicians implement rapid measures to reduce bacterial levels and restore safe water conditions.
We carry out follow-up sampling to verify that Legionella has been eradicated and can help you implement ongoing monitoring for early detection in the future.
All actions are recorded to support compliance with HSE guidance and demonstrate your proactive response. We also provide expert advice for updating your written scheme of control.
Tailored Advice by Sector
Each industry faces unique challenges when it comes to managing Legionella risk. We deliver targeted solutions based on your environment and usage patterns:
- Work closely with infection prevention teams.
- Use of point-of-use filters in critical care areas.
- High-frequency testing and documentation protocols.
- Spa pools, hot tubs, and communal showers receive intensive treatment.
- Guest-facing communication plans to maintain confidence.
- Seasonal building reopening support.
- Cooling towers and complex process water systems require robust, often bespoke, control strategies.
- Solutions that minimise disruption to productivity and ensure worker safety.
- Prompt notification to tenants and property management teams.
- Whole-system disinfection for shared facilities.
- Recurrent risk assessments to maintain compliance.
- Identify and treat areas with stagnant water (e.g., unused taps post-lockdown).
- Support for reopening protocols, especially after long-term closures.
- Ensure safety in dormitories, gyms, and science labs.
- Liaise with local authorities to meet legal duties.
- Guidance for informing staff, students, and parents.
Managing Complex Pipework Systems
Older buildings, large campuses, and multi-use sites often have intricate water systems, which increase the risk of bacterial colonisation. We use advanced techniques to manage these risks effectively:
- System Mapping: We assess water flow and stagnation points to highlight where Legionella may be thriving.
- Specialist Disinfection: High-risk and hard-to-reach areas are treated with customised protocols.
- System Optimisation: We recommend physical improvements, such as pipework modifications or enhanced circulation, to eliminate breeding grounds.