A Brief Guide on Earthing and Bonding

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Earthing system works as an electrical safety system, it’s the process of grounding connective electrical parts to the earth. Earthing or grounding system’s main purpose is to protect you from potential electrical shocks, fire hazards, and unfortunate electrical accidents. 
Earthing is quite different from earth bonding because the second one, its main purpose is only to reduce potential electrical shocks. Earthing is more like the switch-off button, it protects you from getting electrical shocks. 
For example, If your electrical installation is faulty then you are exposed to the danger of getting shocked. Grounding is what keeps you protected because it helps to prevent the electricity from moving into your body to the ground or earth.
You can’t deny how important earthing is for your welfare and your family as well. It also plays a major role in protecting your property’s electrical system and building from potential lightning shocks.
It’s well known that all electrical systems have rules, regulations, and main components to be followed. It helps increase the standard safety and protect appliances from damages, the same goes for earthing and grounding.
In the earthing system, there are three main components: earth continuity conductor, earth leads, and earth electrode.  
  1. Earth continuity conductor: It’s an earth wire that connects all the metallic parts of an electrical installation of your home.
  2. Earth leads: It has limited leads or joints, known as earth joints. Helps to connect the earth continuity and the earth electrode.
  3. Earth electrode: Metallic part with low resistance against faulty buried underground.
  4. Conductors: Usually refers to wires that carry electricity
Now you have a good idea about earthing and grounding, next we will discuss all you need to know about electrical earth bonding. How does it work, and how is it different from the earth system?

What is Bonding?

As mentioned previously, earth bonding reduces electrical power to protect people from current shocks. The main earth bonding connects all the metallic items in your home, like water pipes, gas pipes, or HVAC ducting. 
Those items are considered as items that are not designed to carry any electrical power, which makes them dangerous for you in case of faulty. Earth bonding’s purpose is to eliminate the threat by connecting these items. In the event of any current fault, it reduces the voltages on these items, so you won’t get shocked.
Generally bonding uses two types of earth bonding which are main bonding and supplementary bonding. However, they function the same way, to link to any large metallic items that could be live in case of electrical faulty. 
  1. Current: Refers to moving or flowing electricity
  2. Bonding: The process of reducing voltages and electrical shocks
  3. Live: If an item isn’t designed to carry electricity becomes alive, it means it carries electricity now.

Why do you need Earth Bonding? 

If your building, house, or rental residential gas and water pipes are made from metallic rather than plastic, then you need a pipe or wire earth bonding. You can’t be certain that your wires won’t contact your water and gas pipes. Installing protective or earth bonding reduces the risk of electric shocks, improves your family safety, and prevents financial liabilities from local authorities. 
The UK Regulations dictate that buildings and properties with metallic items not designed to carry charges must install earth bonding. It’s vital for you to have at least one in your home, however, only a certificated engineer must inspect, test, and install wire earth bonding.  
And that takes us to the next point in our discussion.

What will Engineers do?

The first thing an engineer will do is to use an earth bonding tester to test the current resistance on metallic items. The purpose of the bonding test is to measure the current resistance of the connection between an earth cable and the external side of appliances. The device that an engineer uses helps to determine whether your earth bonding system has a satisfactory resistance or not. Usually, there are two types of tests an engineer will do:
  1. Low current: its range is between 100-200 milliamps
  2. High current: Its range is between 10 amps -25 amps
In case of earth bonding unsatisfactory resistance, your engineer will issue a certificate of electrical maintenance. The certificate will include all the electrical issues that your engineer found and that according to the issues UK earth bonding regulations. After receiving the certificate, you are legally required to take immediate action in a duration of up to 28 days. Ignoring your electrical certificate may be costly and you may receive financial penalties. Once you agree to the engineer’s proposal he will start his work and install a new earth bonding.

Main and Supplementary Bonding/ Earthing to Water and Gas Supplies

To prevent undesirable current there are two different aspects or types of earth bonding all buildings must have: 
Main bonding and supplementary bonding.

Main Bonding

On main bonding, engineers use a minimum of 10 mm wire cable to interconnect incoming metallic gas, water, and electrical appliances or services. Water, gas pipes supplies, and electricity services should be bonded only if they are metallic, if a building has plastic pipes supplies bonding isn’t required. All non-electrical metallic parts must be bound and connected to the earth terminal. The main bonding is only required to interconnect the incoming installation in your building
  • Metal water supplies
  • Metal gas supplies
  • All metal services pipes and ducting
  • Metal service heating
  • Air-condition system
  • Lightning protection system

Supplementary Bonding

Usually, supplementary bonding is used to interconnect water pipes, radiators inside your home, rooms, and bathrooms. The purpose of supplementary bonding is to increase your safety level from electric shocks in case you touch two separate live metal parts by accident. 
The regulation dictate that supplementary bonding is necessary for your kitchen to connect the kitchen sink with any metallic pipes in that area.
Supplementary bonding is needed to connect heating suppliers such as central heating boilers, immersion heaters, and combi boilers. 

Difference between Earthing and Bonding

We have noticed that a lot of people get confused when it comes to earthing and bonding working mechanisms. While they seem like the same thing, actually there are not, earthing is quite different from bonding, however, they have the same purpose.
Earthing and bonding share the same purpose of protecting electrical equipment from faulty damages.
Earthing helps in preventing electric shocks in case a person touches live metal pipes. Earthing is the process of grounding electrical connective electrical parts. Meaning all the electrical connective parts must be grounded to the earth by an electrode.
Earthing provides a low resistance path to the earth or the ground, which would protect your electrical equipment and save you from electrical shocks.
While earthing protects you from electric shocks, bonding reduces the flowing current in metal pipes. Bonding connects all metallic items that are not designed to carry electrical power by using a protective conductor with stops any moving current on those items.
Regardless of the differences earthing and bonding have, both are essential installations for you, and your home safety.


Bonding is connecting all the metal items that are not designed to carry electrical power to reduce the risk of electrical shocks.

Earthing and bonding are essential for the safety of your family in case current leak.

It's recommended to avoid doing any bonding tests by yourself, call for a qualified engineer for electrical inspection and he will do the work for you.

In the UK the main cost of earth bonding is between £220-£320, however, the cost could increase depending on your location, your engineer, and your previous wiring system.

There are many factors to take, there is no fixed duration, and mostly it depended on the state of your electrical equipment and their locations.

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Pro Checks Authors

Pro Checks Authors

Pro Checks is a London-based team specializing in landlord safety certificates, including electrical, gas, and fire safety. Committed to delivering high-quality, reliable services at competitive prices, our experienced professionals provide prompt service and attention to detail to meet the needs of landlords and property managers. Choose Pro Checks for all your safety certificate needs and have peace of mind knowing your property is in safe hands.

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