NOT USED Hot Water Risks and Hazards

Risks, hazards and how to mitigate them

The risks associated with domestic water systems include the following:​

• Scalding and burning​
• Carbon monoxide poisoning ​
• Explosion ​
• Corrosion and water damage​
• Legionella disease ​
• Unsafe electricity

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Ensuring hot water safety is vital in residential properties, to safeguard the occupants and preserve the integrity of the building and its structure. Hot water can present a substantial health hazard if not installed correctly and subject to regular inspection and maintenance.

Safety

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Burns and scalds

Carbon monoxide

Legionella

Electrics

Most commonly occurs in baths and showers.

Carbon monoxide (CO) is a silent killer; it is odourless and colourless.

Legionella is a bacteria that grows in water between 20-45 °C.

All modern hot water systems are connected to electrical controls.

Risks to people

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Leaks

Explosion

Leaks are the most common and obvious risk to a building.

An explosion is the most extreme risk with domestic hot water systems.

Risks to buildings

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LOREM IPSUM DOLOR SIT

Risks to the building and fabric

See some of the issues leaks can cause by selecting the icons on the images.

• In both situations repairs should be undertaken immediately to avoid it worsening.

• It may involve landlord or home insurance to cover these sorts of risks.

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Over time, minor leaks such as drips, can cause joists and support structures to weaken. Small leaks can also lead to problems with damp and mould in property.

More significant leaks such as bursts and splits can cause damage more instantly.

• Ceilings can bulge and collapse
• Woodwork can expand
• Electrical safety issues can arise such as short circuits

Risk of explosion

Explosions pose the greatest danger to both occupants and buildings. Safety features like vents and relief valves help manage overheating by releasing water although issues often stem from shoddy work or neglecting maintenance. It takes time for water to boil and change state. Under pressure, water remains liquid at higher temperatures. If this pressure is released, it results in rapid expansion or an explosion - a large volume of water heated above 100 °C, remaining a liquid as it can't escape. Eventually, the pressure will be too great causing a mass amount of water to vaporise into a gas. Read about a cylinder explosion:

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If a cylinder explosion fractures or rips out the gas pipe, this can result in a fire.

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Try a few questions

1. What is the odourless and colourless, poisonous gas produced by incomplete burning of carbon based fuels?

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3. What is the most extreme risk a hot water system can pose to a building?

2. The risk of Legionella increases when water is stored at what temperature?

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• 10°C - 20°C
• 20°C- 45°C
• 40°C - 55°C

• Hydrogen chloride
• Nitrogen
• Carbon monoxide

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• Cylinder explodes
• Boiler leaks acids
• Boiler leaks pressurised boiling water

20°C - 45°C

Carbon Monoxide

Cylinder Explodes!

Know what you're looking at first!

Visually checking a system can provide valuable information about its condition, such as the age and maintenance level of taps, pipework, and appliances. It is also important to refer to technical information or manufacturer instructions to ensure proper installation and service history, including details about the installer and each service performed on the system.

Identify the system type!​

If it has a combination boiler ...

it is a sealed system​

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If the cylinder has an expansion vessel and pressure relief valves...

it is a pressurised unvented system

If the cylinder is in an airing cupboard and storage tanks in the loft...

it is a gravity system

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Know what you're looking at first!

Visually checking a system can provide valuable information about its condition, such as the age and maintenance level of taps, pipework, and appliances. It is also important to refer to technical information or manufacturer instructions to ensure proper installation and service history, including details about the installer and each service performed on the system.

Identify the system type!​

If it has a combination boiler ...

it is a sealed system​

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If the cylinder has an expansion vessel and pressure relief valves...

it is a pressurised unvented system

If the cylinder is in an airing cupboard and storage tanks in the loft...

it is a gravity system

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Correct valve for the correct job!

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Now you know the system's age, type, and history, you can check for defects that might lead to unsafe situations. Key things to check on each system will slightly differ, but it will help to identify possible DIY works, age-related issues, or poor workmanship. Do you recognise these valve types?

Gas Isolation Valve

Water Isolation valve

Lever Isolation Valve

Gate Valve - Low Pressure Isolation

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Things to check​

Check the area for signs of leaks. Wet or damp patches could indicate this.​ Check for signs of scaling on the whole system, this can result in a diminishing of efficiency and a risk of blockages. ​ Listen, run the hot taps and if you hear loud banging or vibrating, the system might not be clipped or supported properly.

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Tradespeople must be occupationally qualified and registered with a competent person scheme to work on hot water systems. If you suspect something is incorrect or unsafe, or you are unsure, seek advice from an approved, qualified plumber.

If in doubt, talk to a professional!!​

Health and Safety considerations​

Hover over the images to reveal the information

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Enclosed spaces such as loft create a risk of falling and Claustrophobia.

Pipework can get hot, there is a risk of burns.

Be aware of water expansion. If you suspect a blockage on a hot water cylinder or the safety valves are not right due to scale. Report it to a qualified plumber.

Electric shock. Boilers and pumps and some controls need power. If they look damaged do not touch them. There could be a risk of electrocution.

Common Visual Faults

EDF Energy: 10 common boiler problems

British Gas: What to do if you have no hot water?

Boiler Guide: Common Hot Water Cylinder Problems

Common Visual Faults Table

Select the images to access the resources

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Legionella causes Legionnaires' disease, which can be a serious illness. To prevent this:

• Systems should be designed and maintained to ensure small runs of pipework.
• Ensure hot water is adequately heated above 45 °C to kill the bacteria and prevent it from growing.

Find out more from the Health & Safety Executive:

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Electrical controls like pumps, immersion heaters, and zone valves depend on electricity to function efficiently. Incorrect installation, such as wrong cables or placing controls in unsuitable areas, can pose electrocution risks. Regular maintenance by professionals such as plumbers, electricians, and gas engineers is essential for safety. It helps prevent issues like poor workmanship, outdated controls, inadequate safety features, and ensures proper electrical earthing. Read more about electrical safety with the HSE:

Burns or scalds happen when hot water comes into contact with the skin, often during activities like bathing or showering. Regulations exist to prevent such accidents, which we'll explore in the following sections. The HSE provides guidance on why water is heated to high temperatures and how to reduce the associated risks.

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Carbon monoxide (CO) poisoning stems from incomplete combustion in heat-producing appliances like boilers, commonly used for heating water in homes. It can occur in both modern pressurised systems and older gravity systems. CO is dangerous because it's odourless and colourless, posing a silent threat that can lead to severe illness or death. Proper installation and regular maintenance of heating systems are crucial in preventing CO poisoning. Installing CO detectors and ensuring adequate ventilation further minimizes the risk.

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Legionella causes Legionnaires' disease. This can result in severe illness. To prevent this:

• Systems should be designed and maintained to ensure short runs of pipework and to
• Ensure that hot water is adequately heated above 45 °C to eliminate the bacteria and prevent its growth.