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It is natural to find legionella bacteria in freshwater lakes and ponds. Some inevitably gets into domestic supplies and in very small quantities it is harmless. It is when it manages to breed and multiply inside our plumbing systems that it becomes dangerous. The lungs are particularly susceptible. Most people think of a pneumonia-like illness when you say legionella, but it can also cause a variety of problems including “Pontiac fever”, “Lochgoilhead” fever, septic shock and organ failure. Legionella is a killer. 

Buildings locked-up or powered-down during the Covid-19 lockdown are now at increased risk because legionella prefers stagnant non-moving water and lukewarm temperatures.

Statutory responsibilities

A legionella infection is more likely in a large building such as an office block, public space, large factory or retail premises, but that does not mean there is zero risk in smaller buildings. In fact, even small landlords are bound by law to protect their tenants.

Big or small - the landlords, employers and managers of public buildings are responsible under a range of legislation. The main three are the Health and Safety at Work Act 1974. the Health and Safety at Work Regulations 1999, and the Substances Hazardous to Health Regulations 1999 (COSHH). Legionella precautions are also required or implied by numerous codes of practice, including HSE Approved Code of Practice ACOP L8 and HSE HSG274, DoE Health Technical Memoranda HTM 04-01 and HTM 01-05 (healthcare and dentistry), and in BS 7592 and BS 8580.

The greatest risks are usually associated with HVAC cooling towers, evaporative condensers, adiabatic coolers and all the associated pumps, tanks and pipework. However, premises of all sizes must comply with the same standards - including domestic landlords and letting agents. In small flats, cheap combi boilers that fail to deliver water at a stable hot temperature are a legionella hazard. High risks also come from stagnant water in shower outlets and clumsily capped pipework spurs.

The regulations apply to showers, vehicle washes, wet floor scrubbers, indoor water features, air washers, humidifiers, water softeners, chillers, spa pools, swimming pools, industrial quenchers, and to all hot and cold water supplies.

If a building occupant or visitor falls sick due to a legionella infection the consequences can be severe; evacuation, rehousing, lost income, new equipment, laboratory testing and compensation. Prevention really is better than the cure!

What you need to do

Begin by checking your basic system and identifying any problem points. It helps to have a schematic for a large building. In a small one, eliminate unused pipework and ensure the boiler/shower delivers a constant flow of hot water (without thermostats tripping on/off). The single most important factor in legionella prevention is to keep your cold water below 20 degrees centigrade, and your hot water close to 60 degrees centigrade or better. 

You cannot guarantee compliance with those temperature requirements if you can’t monitor the temperatures throughout the system. To show compliance, you should document all your temperature readings and all your work on the system.

Making light work of good health!

Regular readings and documentation could be a major headache, however there is a smart solution. Fitting wireless temperature sensors on pipes and at other key locations in the system can enable you to collect temperatures almost constantly and log them automatically. Today there are a range of inexpensive sensors - many so unobtrusive you will hardly know they are there. Most can be fitted externally with negligible inconvenience. Some incorporate accelerometers that also monitor the flow rates.

Smart sensors communicate using the IoT - the internet of things. You can then monitor what is happening via a Cloud dashboard from any computer or mobile phone at any time. If an issue is detected, the system will send you an alert by SMS or email so you don't have to sit there staring at it! Installing smart valves or smart thermostats into your plumbing system adds the ability to remote control the flow rates and temperature settings. In the long run, the opportunity to make water and fuel savings could pay for the system.

The L8 Approved Code of Practice suggests the entire water system should be reviewed every 1-2 years, but sooner when there are relevant changes. Those changes include plumbing work (because dirt can enter the pipework), periods of vacancy (because of stagnation), or temperature fluctuations (tripping thermostats). The presence of anyone at increased risk (with kidney disease, immune system impairment, the elderly and so forth) also constitutes a change meriting more frequent monitoring. If you install a smart connected system, inspections and reviews require very little work at all.