How to Prevent Legionella: A Guide to Managing Hot and Cold Water Systems

Legionella is a serious threat, but with the right knowledge and consistent effort, you can significantly reduce the risk of Legionella contamination in your home, business, or any building. These microscopic organisms are the culprits behind Legionnaires’ disease, a severe form of pneumonia that can be fatal.

The good news is that Legionella prevention is entirely possible by understanding the conditions in which the bacteria thrive and implementing effective control measures. This guide will walk you through the best practices for Legionella control and provide you with a comprehensive understanding of how to prevent Legionella in various settings.

Understanding the Enemy: What is Legionella?

Legionella bacteria are a type of germ found naturally in freshwater environments like lakes and rivers. However, they become a health risk when they grow and multiply in human-made water systems like plumbing, cooling towers, and other artificial water systems.

The specific strain most commonly associated with Legionnaires’ disease is Legionella pneumophila. The infection occurs when people inhale tiny, airborne aerosolized water droplets containing the bacteria. These droplets can be created by a shower, a cooling tower, or even a decorative water feature.

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The conditions that lead to Legionella bacteria growth are very specific:

1. Stagnant water: Water that sits still for long periods allows bacteria to multiply.
2. Optimal temperatures: Legionella thrives in water temperatures between 20°C (68°F) and 45°C (113°F). Temperatures outside this range inhibit their growth.
3. Nutrients: Biofilm, rust, and other organic matter in water provide a food source for the bacteria.

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Essential Legionella Prevention Methods for All Buildings

The cornerstone of Legionella prevention in buildings is a robust Water Management Program. This is not just a good idea; it’s a critical Legionella risk management strategy. The program should include a Legionella risk assessment to identify potential sources of contamination and a detailed Legionella prevention plan outlining specific actions to mitigate those risks.

1. Temperature Control

Maintaining proper water temperature is one of the most effective Legionella safety measures you can implement. The bacteria thrive within a specific temperature range, so by keeping your water either hot enough to kill them or cold enough to inhibit their growth, you can effectively control their spread.

Effective temperature solutions include:

• Hot Water Systems: Your hot water storage cylinders or hot water tanks should be set to a temperature that kills Legionella. The recommended temperature for a domestic hot water system is to store water at 60°C (140°F) or higher and distribute it at a minimum of 50°C (122°F). Make sure all hot and cold water outlets reach these temperatures. Regularly check the water heaters to ensure they are functioning correctly.
• Cold Water Systems: Cold water storage tanks and cold water pipework must be kept consistently cool. The temperature of cold water should be kept below 20°C (68°F) to prevent the growth of Legionella bacteria. This often means ensuring that cold water tanks are not located near heat sources and that cold water pipework is properly insulated.

2. Preventing Stagnation and “Dead Legs”

Stagnant water is a breeding ground for Legionella. When water sits still in pipes for long periods, it allows the bacteria to multiply to dangerous levels. A key Legionella prevention and control measure is to ensure water is constantly moving throughout your system.

Prevent Stagnant water and the spread of Legionella by:

• Flushing Outlets: Regular flushing of rarely used water outlets, such as showers, taps, or hoses, is crucial. If a tap or shower hasn’t been used for a week, run the water for a few minutes to flush out any potential Legionella bacteria.
• Eliminating Dead Legs: A “dead leg” is a section of pipework that no longer serves a purpose, leading to stagnant water. These should be identified and removed by a qualified professional as part of your Legionella prevention in plumbing.

3. Regular Cleaning and Disinfection

Over time, sediment and biofilm can build up in water tanks and pipes, providing nutrients for Legionella. This organic matter creates an ideal environment for the bacteria to thrive, making routine cleaning and disinfection a critical part of a comprehensive Legionella prevention plan.

Cleaning to avoid the presence of Legionella entails:

• Thermal Disinfection: A thermal disinfection solution involves raising the water temperature in a system to a high level (e.g., above 60°C) to kill the bacteria. This disinfection process is often a key part of a maintenance plan.
• Chemical Disinfection: Chemical treatments, like chlorine, can also be used to disinfect a system. This should be done by a qualified professional.
• Cleaning Water Tanks: Hot and cold water storage tanks should be inspected and cleaned regularly to remove any sediment.

4. Maintaining High-Risk Systems

Certain systems pose a higher risk of Legionella contamination and require special attention. Because these systems can create and aerosolize water droplets, they have a greater potential to spread Legionnaires’ disease. Proper maintenance is therefore essential to mitigating this risk.

Water systems at risk of developing Legionella include:

• Cooling Towers and Air Conditioning Units: Cooling towers and large air conditioning systems are notorious for creating the perfect conditions for Legionella to multiply and become airborne. These systems require a stringent maintenance schedule, including regular cleaning, biocide treatment, and inspection of water collection pans and water reservoirs. Air conditioning units and their internal water sump must also be properly maintained.
• Water Softeners: While helpful for preventing scale, water softener units can sometimes create conditions for bacterial growth if not properly maintained.
• Water Features: Decorative water features can aerosolize water and should be managed with proper filtration and disinfection.

Staying on top of your water system is essential to prevent the spread of Legionella. Talk to our experts to decide the best plan of action! 

How to manage legionella in hot and cold water systems

Legionella Prevention for Landlords and Businesses

Landlords and property managers have a legal and ethical responsibility to ensure the safety of their tenants. The Legionella prevention guidelines for landlords are particularly important. The following practices can help landlords and business owners stay compliant and keep all tenants and employees safe from Legionella:

Legionella Risk Assessment

You must have a Legionella risk assessment conducted by a competent person. This identifies potential risks in the Building Water Systems and provides recommendations for a Legionella prevention plan.

Regular Monitoring

Implement a system for monitoring water temperatures and ensuring they are within safe ranges. Keep a water log book to record all checks and maintenance activities.

Communication

Inform tenants of any Legionella safety measures they should be aware of, such as the need to flush taps after returning from a holiday.

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Why You Should Invest in a Professional Legionella Risk Assessment?

While some businesses or landlords may attempt a DIY approach, a professional Legionella risk assessment is a crucial investment. It goes beyond a simple checklist, providing a thorough and expert analysis of your building water systems to identify hidden risks and ensure you are fully compliant with all legal requirements.

1. Legal Compliance and Due Diligence: A professional assessment helps you meet your legal obligations as a duty holder or landlord. It demonstrates you have taken all reasonable steps to protect occupants, which is vital in the event of an outbreak and can prevent prosecution and heavy fines.
2. Expert Identification of Risks: Trained professionals have the experience and knowledge to identify subtle risks that a layperson might miss. They can spot issues like complex pipework, dead legs, and inadequate water temperature control that contribute to Legionella bacteria growth.
3. Tailored and Comprehensive Plan: A professional service doesn’t just identify risks; they provide a customized Legionella prevention plan. This plan outlines specific, prioritized actions and Legionella safety measures for your unique system, ensuring you focus on the most critical issues first.
4. Provides Peace of Mind: Engaging water safety specialists provides reassurance that your property is as safe as possible from the threat of Legionnaires’ disease. You receive an official report and a clear action plan, giving you confidence and protecting the health of your occupants.

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Understanding Legionella risk assessment cost

LegionellariskandPAT.com: Your Partner for Legionella Risk Assessments in Scotland

As specialists in Legionella Risk Assessment and PAT Testing for commercial and domestic properties, we offer a service designed for your peace of mind. We provide comprehensive, fixed-price Legionella risk assessments starting at just £55, making us one of the most cost-effective options in Scotland. Our service not only helps you meet your legal obligations but also delivers a professional, detailed report that demonstrates your commitment to safety and compliance.

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