How to Manage Legionella in Hot and Cold Water Systems

25 June 2024

Legionella is a bacteria that can cause potentially fatal illness. For this reason, water systems must undergo a risk assessment and be maintained with regular inspections, water testing and water tank cleaning to ensure safe water quality and minimise legionella risks.

Read on to learn more about managing legionella in hot and cold water systems.

What Is Legionella?

Legionella is a type of bacterial commonly found in water. This bacteria can multiply in water between 20 and 45℃, contains nutrients and is stagnant. If a person ingests water droplets with viable legionella bacteria it can cause them to contract Legionnaires’ disease, a severe form of pneumonia.

While anyone can contract Legionnaires’ disease, it often proves more serious for the elderly, smokers or those with pre-existing conditions like diabetes, cancer or respiratory or kidney disease.

Risk Assessment

Conducting a Legionella Risk Assessment (LRA) is a legal requirement under the Health and Safety at Work Act 1974. Carrying out a legionella risk assessment will identify your system's risk of legionella growth. This will determine whether current measures are adequate or identify any improvements required to reduce the risk of legionella in your water system.

Temperature Control

Water services should be operated at temperatures that prevent legionella growth.

Cold water must be stored and distributed below 20℃.
Hot water must be distributed at or above 50℃.
Hot water storage cylinders must be stored at or about 60℃.

Hot water tanks should be checked monthly and cold water tanks should be checked bi-annually to ensure all water is stored and distributed at the correct temperature.

Water Testing

Periodic legionella water testing is vital to ensure proper compliance with legislation, including ACOP L8, HSG274 and HTM 04-01. The risk assessment will determine the frequency with which testing should be conducted. If any measures are deemed ineffective, testing should be carried out weekly until the system is under control and legionella is managed.

Water Tank Cleaning

Water tank cleaning helps to manage the risks of legionella. Water tanks and outlets should be effectively descaled every few months to remove nutrients that legionella bacteria can feed off.

Water Treatment

Copper and silver ionisation and biocide treatments can be used to treat legionella in water systems. This treatment can form part of a water management programme, including installation, maintenance and monitoring to ensure measures remain effective at mitigating legionella risks.

Caledonian Heating & Plumbing Ltd

At Caledonian Heating & Plumbing, as members of the LCA (Legionella Control Association), we can help your business ensure that your water systems are safe and compliant with current regulations. From legionella risk assessments to scheduling water testing and tank cleaning, we have a range of legionella management plans to suit businesses of all sizes.

For more information about our legionella services, get in touch today.

< Older Post

Newer Post >

How Often Should Water Tanks Be Cleaned?

27 January 2026

Learn how often commercial water tanks should be cleaned to maintain water quality, manage legionella risk and stay compliant with UK regulations.

Why Planned Maintenance Beats Emergency Repairs Every Time

27 January 2026

Planned maintenance for commercial heating in Scotland reduces costly breakdowns, downtime, and ensures efficiency, safety, and compliance.

Why Water Risk Assessments Are Vital in Healthcare Settings

18 December 2025

Ensure patient safety and compliance with expert water risk assessments in healthcare. Prevent Legionella and protect your facility’s reputation.

Emergency vs Routine Plumbing Repairs: When to Call the Experts

19 November 2025

When it comes to plumbing issues, timing is everything. A small leak can quickly turn into a major problem if left unchecked, while some situations demand immediate attention to prevent costly damage or business disruption. Understanding the difference between emergency and routine plumbing repairs can save you time, stress, and money, and help you know when it’s time to call in the experts. What Counts as a Plumbing Emergency? A plumbing emergency is any issue that poses an immediate risk to safety, property, or business operations. In commercial environments, even a short period of downtime can have serious consequences, so swift action is essential. Common plumbing issues include: Burst or leaking pipes – Sudden water leaks can cause flooding and damage walls, floors, and electrical systems. Blocked or overflowing drains - Particularly in high-traffic areas, this can create health hazards and disrupt operations. No hot water or heating - Especially critical in settings like schools, hospitals, or care facilities. In these situations, it’s vital to contact a qualified plumbing engineer right away. Our team at Caledonian Heating & Plumbing provides rapid-response emergency support to restore safety and minimise downtime for commercial clients. When Is It a Routine Repair? Routine plumbing repairs cover non-urgent maintenance tasks or issues that develop gradually. While they might not cause immediate disruption, they still need attention to prevent bigger problems later on. Examples of routine repairs include: Slow-draining sinks or toilets Minor leaks under basins or radiators Reduced water pressure Regular maintenance of heating systems or water tanks Scheduling routine repairs ensures your systems continue running efficiently and helps you plan maintenance at a time that suits your business, avoiding the cost and chaos of unexpected emergencies. The Benefits of Preventative Maintenance Many plumbing emergencies are avoidable with regular inspections and servicing. Planned maintenance helps identify potential issues before they escalate, ensuring your systems remain compliant, efficient, and reliable. At Caledonian Heating & Plumbing, we tailor maintenance schedules for each client, from small businesses to large facilities, to keep everything flowing smoothly year-round. Proactive maintenance also supports compliance with health and safety regulations, such as ACOP L8 for water systems and Gas Safe standards for heating installations. When in Doubt, Call the Experts If you’re unsure whether an issue is urgent, it’s always best to speak with a professional. Attempting DIY fixes or delaying repairs can lead to greater damage, increased costs, and potential safety risks. At Caledonian Heating & Plumbing, our engineers are on hand to assess the situation and provide the right solution, whether that means an emergency call-out or scheduling routine maintenance at your convenience. Need urgent help or want to arrange a maintenance visit? Contact Caledonian Heating & Plumbing today for expert, reliable service across Scotland.