The gas central heating guide

Your central heating system supplies your household with heat and hot water - essential home comforts that help make life a lot more agreeable.

Here, you’ll find out more about gas central heating appliances, how to ensure your gas central heating system is properly installed and maintained by a Gas Safe registered engineer, and the warning signs of an unsafe gas central heating system.

What is gas central heating and how does it work?

Most of us here in the UK use a mains gas central heating system, sometimes called a ‘wet system’, to keep ourselves and our homes warm and comfortable.

This type of system works by using a gas boiler to provide heat in your home through radiators and hot water through taps. There are different kinds of gas boilers for central heating, and you can find out more about these by taking a look at our dedicated boiler guide.

At the centre of a ‘wet central heating system’, a boiler burns gas which heats the water feeding a network of pipes connected to your home’s radiators and a hot water tank.

Gas central heating isn’t the only option for homes in the UK. Households which aren’t connected to the mains natural gas network might use electric central heating, LPG or oil central heating systems.

What are the pros and cons of gas fuelled central heating?

If you’re thinking of getting gas central heating installed in your home, then you’ll want to consider the advantages and disadvantages first.


  • Modern condensing boilers are extremely efficient
  • It is relatively simple to replace a standard gas boiler with a high efficiency condensing boiler
  • Mains natural gas systems are piped directly into your home; there’s no need to store it


  • Gas central heating systems often have a higher upfront cost that other systems, such as electric but lower running costs long term.
  • It may be expensive to get your home connected to the gas network if it’s not already

Gas central heating installation

If you’re having a gas central heating system installed in your home, this needs to be done by a competent Gas Safe registered engineer.

It’s the law that gas engineers to be registered with Gas Safe Register. This shows they’ve undertaken at least one industry recognised & accredited competencies to work with gas. However, not all engineers are qualified or competent to do all types of gas work; you’ll need to check their Gas Safe ID card to make sure they have the right qualifications to work on a gas central heating system.


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If you don’t already have a boiler your central heating installer will be able to advise you on the best type of boiler to use in your home. This will ensure it can meet the heating demands put on it by the size of your home.

Your gas boiler is the central component in your gas central heating system, and as a heat-producing appliance, it needs to be approved as safe and appropriate for use under the Building Regulations.

These regulations are not only designed to ensure buildings in the UK are safe to use and inhabit, but they relate to energy efficiency too. Under Building Regulations approved document L1 (A/B), domestic boilers installed in existing dwellings must have a minimum efficiency of 92% under the Energy-related Products (ErP) Directive, and in new dwellings a SEDBUK 2009 efficiency of 88%.

Once your Gas Safe registered engineer has installed your central heating system, they will need to let the relevant local authority know within 30 days, so that a Building Regulations Compliance Certificate can be issued.

If you’re a homeowner, it’s up to you to check your boiler has been notified by your engineer.

Gas central heating servicing and maintenance

An unsafe or improperly maintained gas appliance could put you and your household at risk, which is why it’s important that any gas appliance in your home is correctly maintained by a Gas Safe registered engineer.

This includes the gas appliances in your gas central heating system. Regular servicing and maintenance of your gas central heating system by a competent central heating engineer will ensure your appliances stay in good working order and are safe for continued use in your home.

What does a central heating service involve?

Regular servicing of your gas central heating system will ensure it stays in good shape and is safe to use. Unless otherwise stated in the manufacturer’s instructions, you should ensure your gas appliances have an annual service completed by a Gas Safe registered engineer.

As the main heat-producing gas appliance within your central heating system, safety checks on your gas boiler - in line with the manufacturer’s instructions - will form a crucial part of your central heating systems ongoing performance. You can find out more about boiler servicing and maintenance within our boiler guide.

After your engineer has carried out a service on your boiler you can ask them to provide you with a service report, or Gas Safety Record, detailing all the checks that were made and any work carried out.

During your gas central heating service your engineer may check your radiators and pipework to ensure this is in good working order. If you would like this done, please ensure you let your engineer know.

Gas central heating system maintenance tips

While it’s important to have your gas central heating system regularly serviced by a Gas Safe registered engineer, there are a few steps you can take to keep your system working safely and efficiently in the meantime:

  • Check the central heating system water pressure where applicable - Boilers can lose system pressure as they age. Check the pressure gauge and top it up if it’s too low
  • Bleed excess air from your radiators - You can tell if your radiators need bleeding if they’re colder at the top than the bottom, meaning excess air is trapped in the system, putting extra strain on your boiler
  • Lag the pipes - When it gets very cold your boiler’s external condensate pipe can freeze and your boiler will cut out. You can prevent this by asking a Gas Safe engineer to insulate your condensate pipe

Even with proper maintenance on your part, the best way to keep your gas central heating system working safely and efficiently is by using a Gas Safe registered heating engineer to complete regular gas safety checks and servicing.

Signs of an unsafe gas central heating system

A problem with your gas central heating system has real potential to put you and your household at risk.

If you can smell gas, can see visible scorching, sooting or black marks, or a floppy yellow pilot light on your boiler, or if you or anyone in your household has been feeling unwell and experiencing headaches, nausea or dizziness, it’s crucial to act quickly.

Get out of the property, turn the gas off if safe to do so and contact your gas emergency service. You could find the numbers to call on our What to do in a gas emergency web page.

Carbon monoxide (CO) is a highly poisonous gas produced by the incomplete burning of natural gas or liquefied petroleum gas (LPG). This can happen when a gas appliance has been incorrectly fitted, badly repaired or poorly maintained.


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