Cuts in maintenance budgets and mutating legionella bacteria are a nasty combination for building occupants, warns Bob Towse.
At least 9,000 people catch Legionnaires' disease every year. That figure might sound high, but many cases are misdiagnosed so the official figure is considerably lower. The symptoms can be very similar to flu, but it will kill in 12 per cent of cases.

Among the old and infirm the fatality rate is close to 50 per cent. These days we know a lot about the legionella bacteria that leads to outbreaks of the disease, but many experts believe that the bug is mutating and can, in some instances, survive in water that meets current safe temperature guidelines. It is also showing resistance to some of the chemicals designed to kill it. There are also growing problems with the way in which water systems in care homes, hotels, schools and a host of other establishments are monitored and treated. Simon French, a legionella expert and member of the HVCA's Service and Facilities Group, says: 'Legionnaires' disease is far more common than many people think. Everyone associates it with cooling towers, but it has also been discovered in car washes, windscreen water, dental chairs, and even compost heaps.

'But by far the greatest risk lies within the humble hot and cold water systems, which deliver the disease through taps and shower heads.Legionella bacteria thrive in temperatures between 20-45 deg C; and if water is allowed to sit at these temperatures the bacterium can multiply into large numbers which cause Legionnaires' disease.'

And some new strains of the bacteria have been known to survive in temperatures up to 61 deg C. As with many other aspects of building maintenance water treatment, that guards against the threat of legionella build up, is suffering from budget cuts. There is also growing evidence that many logbooks, designed to identify the dangers in temperature 'breeding zones' within internal pipework, are not being filled in properly.

However, as well as protecting health, a planned and well organised water treatment regime will also reduce building running costs so giving owners an excellent and rapid return on what is a pretty modest investment.

If water heating systems are shut down for periods, or hot water temperatures lowered, to save energy this could create the perfect breeding conditions for the bacteria. These can then be spread to potential victims as an aerosol via showers and taps. There is also an emerging threat from rainwater harvesting systems that store large amounts of water that could already be contaminated.

Specialist contractors are urged to refer their clients to the Health and Safety at Work Act, which outlines a building owner's responsibilities in this area.

Also, the HSE's Approved Code of Practice L8 (ACOP) and guidance 'Legionnaires' disease - the control of legionella bacteria in water systems' is available for download free from: www.hse.gov.uk/pubns/books/l8.htm. This provides detailed guidance on avoiding the main threats posed by legionella bacteria. Accurate record keeping, corrective action and complete audit trails are key parts of the guidance.

There is also a new British Standard (BS8580), which focuses particularly on the issues surrounding rainwater harvesting systems.

Many HVCA members now offer 'continuous dosing' systems, designed to maintain water systems in a permanent state of excellent hygiene - 24 hours a day/365 days a year. These systems release controlled levels of chemical treatment into the water system at a set times, or in response to changing conditions, so removing some of the potential for human error or omission.

As well as minimising health threats, this approach will also dramatically improve a system's operating efficiency.

For example, systems that are continuously maintained suffer from fewer breakdowns, so reducing the need for costly repairs. Also, if a system is continually dosed the water does not need to be held at high temperatures in order to guard against legionnella build up.

This is a major energy saving. Many schools, for example, leave their water heating running even during holidays and weekends to maintain the system above 60degC. They would not need to if the system was continuously treated.

Reducing water temperatures has other benefits. High temperatures lead to more scale build up and scale acts as insulation inside pipes and heat exchangers so reducing heat transfer.

Each millimetre of lime-scale is estimated to reduce energy efficiency by eight per cent. Keeping systems at lower temperatures also reduces the risk of scalding - without the need for thermostatic mixing valves - and planned bacteriological protection reduces the hazard of 'dead legs' in pipe work. There is a pressing need for everyone involved in building maintenance and management to understand where the health risks lie and what the energy penalties could be with poorly maintained hot water systems. However, in an era of reduced staff and budgets, and higher workloads, there is more room for human error. For example, monthly manual temperature checking and manual flushing can be left out or completed in haste. And even if monthly checks are meticulous, who knows what is happening, day-in-day-out, as temperatures fluctuate within any system? Legionnaires' disease may come and go from our national headlines, but its potential for harm is as present as ever and cannot be ignored by any responsible building owner.

•Bob Towse is head of technical and safety at the HVCA