Controlling Hot Water: The Balance Between Legionella Bacteria and Scalding

A tourist tragically died in 2012 after being scalded by the shower in her hotel room. The hotel was sued for a six-figure sum, with the family’s solicitor arguing that the hotel failed in their duty of care.

On holiday with her family from India, Kalyani Uthaman was in intensive care for six weeks having suffered 25% burns to her body. She later died from multiple organ failure which doctors claim was caused by her injuries. Her family sued the national hotel chain to pay for her hospital treatment.

The family’s solicitor argued that the hotel failed in its duty of care by not having a thermostatic mixing valve fitted, while the hotel maintains that despite settling out of court, that it was an “isolated incident”.

All owners or managers of a building that is used by third parties (anyone other than the owner), have a duty of care to ensure that others can use the building and its facilities safely.

Thermostatic mixing valves (TMVs) became a legal requirement when the Building Regulations were amended in 2012. Since then, TMVs have been required in all new dwellings and any dwellings that undergo a change of use. However, existing buildings remained exempt from the change.

When speaking to the BBC, Mrs Uthaman’s family solicitor commented: “While the regulations say [the valves] only need to be installed in buildings constructed after 2006, we believe there is a case in common law that the hotel failed to properly care for Mrs Uthaman.”

The fitting of thermostatic mixing valves in all buildings where there are occupants other than the owner is a recommendation in the Recommended Code of Practice for Safe Water Temperatures published by the Thermostatic Mixing Valve Manufacturers Association. The recommendation is also backed up by the HSE and the NHS Estates Guidance Note for Safe Hot Water.

Around 20 people in the UK die each year as a result of scalding from hot water and 570 people suffer injuries.

Most of these injuries can be prevented from happening by the installation and usage of appropriate safety products and procedures. With the majority of occupied buildings in the UK served by hot water storage and distribution systems, there are pre-existing preventative measures that can be taken fairly simply – one being the installation of TMVs.

Even if TMVs are not fitted, risk assessments and the necessary actions should be carried out on an individual basis to ensure that building owners are fulfilling their duty of care.

When it comes to water temperature control, there are two major concerns: scalding from hot water and legionella bacteria.

While both risks arise from the storage and delivery of hot water, the preventative measure put in place for one usually increases the risk for the other. For example, turning down the hot water temperature so that it does not scald makes it the perfect temperature for legionella bacteria to grow. But water temperatures that kill the legionella bacteria are hot enough to scald, making it a catch 22 situation.

But there is a solution.

The temperatures at which scalding occurs are constant, but the degree of potential scalding has variating factors. The degree of scalding will be determined by the actual temperature of the water, the volume of delivered water, and the contact time between the water and skin.

The NHS Estates Health Guidance Note recommends the following temperatures for delivered water to avoid scalding:
● 46°c for an assisted bath fill
● 44°c for an unassisted bath fill
● 41°c for showers and basins
● 38°c for bidets

Legionella Bacteria
As soon as you turn the water temperature low enough so that it will not scold, it becomes cool enough for legionella bacteria to grow. And it can grow within both the storage and distribution systems.

Legionella bacteria are naturally occurring organisms and water temperatures above 60°c will kill them. This is why hot water should be stored and distributed above 60°c.

Legionella bacteria will rapidly multiply in water temperatures between 20°c and 45°c. However, they will not multiply in water temperatures lower than 20°c, although they may remain a threat in the system. Therefore, all cold water supplies should be stored and distributed at temperatures below 20°c.

Exposure to the legionella bacteria can cause the development of Legionnaires Disease.

It is possible to provide safe hot water, by controlling the temperature of the delivered, distributed and stored hot water.

Ideally, the hot water will be stored above 60°c, distributed at 55 – 60°c and reduced using a thermostatic mixer valve to a delivery temperature of 35 – 46°c.

This will reduce the risk of both legionella bacteria growing, and the risk of scalding.

A TMV is designed to accurately control the delivered temperature of hot water used for bathing, showers, basins and bidets. It does this by mixing the hot water supply with a cold water supply, keeping it consistent even when the incoming water pressure or flow fluctuates.

TMVs are designed to automatically shut down in the event of a cold water supply failure to prevent the release of scalding hot water. They will also shut down in the event of a hot water supply shortage to prevent the potential of thermal shock.

Building managers and owners have a responsibility to provide a duty of care to any third party using the premises. How you do that is up to you – whether it be by individual risk assessments or the retrospect fitting off thermostatic mixing valves. But remember, the change to Building Regulations in 2012 means that it is now a legal requirement to fit TMVs to any new building or any building which has had a change of use.

With the use of TMVs, you can help protect anyone who visits and uses your building from both legionella bacteria and scalding – both of which can be life-threatening. You can safely store water at temperatures that kill legionella bacteria, yet deliver the hot water at temperatures which do not scald.

Article written by Ideal Heat Solutions

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