Tourist Kalyani Uthaman tragically died in 2012 after being scalded by her shower. She was staying at a Scottish hotel, while on holiday from India with her family.

Having suffered 25% burns to her body, Kalyani was in intensive care for six weeks. She later died from multiple organ failure, which doctors claim was caused by her injuries.

Every year, around 20 people die as a result of scalding from hot water. And while the hotel’s owner maintained that it was an “isolated incident”, the family’s lawyer argued that the hotel failed in its duty of care by not having a thermostatic mixing valve fitted.

In a statement to the BBC, the family’s solicitors commented: “While 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.”

Duty of Care

If you own or manage a building that is used by third parties (ie. anyone other than the owner), then you have a duty of care to ensure that others can use the building, and its facilities, safely.

Amended in 2012, building regulations changed to state that thermostatic mixing valves are now a legal requirement in all new dwellings and any dwellings that undergo a change of use. However, existing buildings remained exempt from the change.

The fitting of thermostatic mixing valves (TMVs) 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.

The Risks of Water Temperature Control

Every year, around 20 people die as a result of scalding from hot water in the UK. And around 570 people suffer injuries. But most of these injuries could be prevented.

The majority of occupied buildings in the UK are served by hot water storage and distribution systems, and with the installation and usage of appropriate safety products, unnecessary injuries can be avoided.

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.

Scalding Vs. Legionella Bacteria

Scalding and legionella bacteria are the two major concerns when it comes to water temperature control and safety.

Both risks arise from the storage and delivery of hot water. But 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 water is stored at a temperature low enough as to not scald, legionella bacteria can grow. And it usually grows within the water 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.

In water temperatures between 20°C and 45°C, the legionella bacteria will multiply rapidly. However, they will not multiply in water temperatures lower than 20°C, although they will 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.

The Solution

Safe hot water can be provided 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°C – 60°C and reduced using a thermostatic mixer valve to a delivery temperature of 35°C – 46°C.

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

A thermostatic mixer valve (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 crucial for delivering hot water safely. They are designed to automatically shut down in the event of a cold water supply failure to prevent the release of scalding hot water. And they will also shut down in the event of a hot water supply shortage to prevent the potential of thermal shock.

Final Thoughts

Whether you decide to install thermostatic mixer valves is up to you, but it is your responsibility to provide a duty of care to the occupants of your building. The change to Building Regulations in 2012 also now states it is required by law 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 legionella bacteria killing temperatures of 60°C, yet deliver at temperatures which will not scald.