Understanding gas meter earthing can be confusing, especially because earthing and bonding are often used interchangeably when they actually serve different purposes. For electricians, gas engineers and homeowners dealing with electrical work, knowing the difference is important because the correct arrangement can play a role in keeping an installation safe.
A gas meter itself isn’t simply something that is “earthed” because it contains metal. The real issue is usually whether the associated metallic gas pipework needs main protective bonding and, if so, where that connection should be made. That distinction becomes particularly important when inspecting an older property or carrying out electrical alterations.
What Do the Gas Meter Bonding Regulations Actually Require?
Under BS 7671, main protective bonding is required where metallic pipework is an extraneous-conductive-part. The purpose is to prevent the pipework from introducing a dangerous potential into the installation.
There is no blanket rule saying that every gas pipe in every property must automatically be bonded. The electrical characteristics of the pipework and the way the service enters the building have to be considered.
For example, Electrical Safety First guidance states that where incoming service pipework, such as gas or water, is plastic, protective bonding isn’t required simply because the pipe enters the building. Metallic sections need to be assessed to establish whether they are extraneous-conductive-parts.
This is one reason an engineer shouldn’t make assumptions based solely on what the pipe looks like.
Where Should Gas Pipe Bonding Be Connected?
Location is another area where mistakes can occur.
Where the gas meter is inside the property and the incoming semi-rigid pipe ends at the meter, the bonding connection would normally be made to the consumer’s hard metallic pipework after the meter and before any branch pipework. Where practicable, the connection should be within 600 mm of the meter outlet union.
If the gas meter is installed outside in a wall-mounted or semi-concealed meter box, the connection should generally be made to the consumer’s metallic pipework before branch pipework and, where practicable, at the point where that pipework enters the building.
That detail matters. The bonding connection isn’t simply placed on whichever section of pipe is easiest to reach.
Can You Bond the Incoming Gas Pipe?
This is where the type of pipe becomes particularly important.
Electrical Safety First guidance specifically advises that no attempt should be made to make a bonding connection directly to semi-rigid gas pipework. Instead, where appropriate, the connection is made to the customer’s hard metallic pipework on the correct side of the meter.
A common mistake is to see a metal-looking section near the meter and assume it is automatically the correct place for the bonding clamp. The installation needs to be understood first.
This is also why work around gas installations shouldn’t be approached as a simple DIY electrical task. Gas and electrical systems can interact in ways that aren’t obvious from a quick visual inspection.
What Size Should the Bonding Conductor Be?
Conductor sizing is another area where online advice can become confusing because the correct size depends on the installation and the requirements being applied.
BS 7671 contains requirements for main protective bonding conductors, and the supply arrangement can affect the calculation. Electrical Safety First’s current guidance also notes that some electricity distributors have requirements that exceed the general requirements of BS 7671, so local distributor requirements should be confirmed before work begins.
That means there isn’t a sensible one-size-fits-all answer that should be applied to every property.
For an electrician inspecting an installation, the existing earthing arrangement, bonding, supply type and distributor requirements all need to be considered rather than choosing a conductor based on what was used in another house.
What About Older Gas Installations?
Older properties are where questions about gas meter earthing and bonding often come up.
An installation that doesn’t match the latest edition of BS 7671 isn’t automatically unsafe simply because the regulations have changed. Electrical Safety First notes that existing installations complying with an earlier edition may not meet every requirement of the current edition, but that does not automatically mean they need upgrading.
The situation changes if electrical work is being added or altered. The safety of new work can depend on having adequate existing earthing and bonding arrangements. Electrical Safety First advises that these arrangements should be checked before relevant electrical work proceeds.
So an electrician shouldn’t simply label an older installation as dangerous without assessing what is actually present.
What Should an Electrician Check?
A proper inspection should look beyond the presence of a green-and-yellow conductor near the gas pipe.
The engineer needs to establish whether the gas pipework is an extraneous-conductive-part, where the bonding connection is located, whether the connection is accessible for inspection and testing, and whether it has been made before branch pipework where required.
The condition of the conductor and connection also matters. Electrical Safety First’s guidance identifies inaccessible main protective bonding connections and connections made after branch pipework as issues that can require attention.
This is why simply asking, “Is the gas pipe bonded?” doesn’t always give you a useful answer. The arrangement itself needs to be checked.
Why Getting the Arrangement Right Matters
Bonding isn’t there to make the gas installation part of the electrical system. Its purpose is to help control the potential difference between conductive parts during an electrical fault.
If you’re having electrical work carried out, the existing earthing and bonding arrangements should therefore be checked before the new work relies on them. Electrical Safety First specifically highlights the importance of adequate earthing and bonding for the safety of electrical alterations.
For homeowners, the safest approach is straightforward: don’t add, remove or relocate a gas bonding connection based on advice from a generic online diagram. Get the installation assessed by a suitably qualified electrician who can determine what the property actually requires.
Final Thoughts
Understanding gas meter earthing is really about looking at the complete installation rather than assuming every gas meter should be treated in exactly the same way. The type of pipework, earthing arrangement, location of the bonding connection and requirements that apply to the property all need to be considered.
The gas meter bonding regulations may seem complicated at first, but the principle is fairly straightforward: assess the installation properly, make sure any required bonding is correctly positioned and avoid making changes based on assumptions. If you’re unsure about an existing arrangement, having it checked by a suitably qualified electrician is a much safer approach than relying on a generic diagram or a quick online answer.