Boiler flue regulations in the UK

boiler flue regulations

Gas boilers are the most popular way to heat water and rooms in your home. While they offer many benefits, it is scary to discover that gas boilers burn natural gas and can emit carbon monoxide and other harmful gases.

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This could cause serious injury or in the worst-case scenario death if they aren’t installed correctly. Gas Safe registered engineers adhere to strict rules during installation, especially with boiler flues, to keep you safe, and your boiler running efficiently.

Boiler flue regulations were created to protect you and your neighbors from toxic gases. These regulations are helpful in planning a new boiler installation and ensuring any waste gases expelled leave your home heating systems safely.

What’s a boiler flue and what do they do?

Gas boilers heat your home by burning natural gas. The boiler flue is an attached pipe to the boiler. It allows the gaseous fumes from the burning of the gases from the boiler to escape the building, usually through an external wall.

The boiler flue must be installed in accordance with the boiler flue regulations. This is to ensure safety and avoid carbon monoxide poisoning. The gas safety inspections include an annual inspection of the boiler flue position. Due to the health risks associated with expelled gases, boiler flue regulations have become more stringent over the years.

What types of boiler flues are there?

Gas boiler flues are visible coming out of buildings from the sides, usually through the wall closest to the boiler. You may have noticed steam from your neighbor’s or your own house. This is especially true during colder weather. These are also known as horizontal flues.

Depending on the type and shape of the building, the gas boiler flue may be vertical and exit through the roof. These are known as vertical flues. Modern boilers have an angled flue top, while older boilers have square flues. A new boiler flue should always be included in any new combi boiler cost including installation.

What regulations govern boiler flue?

Condensing boiler flue sitting regulations

Condensing boilers produce gas that is similar to traditional boiler gases. The flue gases consists mainly of water vapour and carbon monoxide.

Gas condensing boilers, however, are cooler. This means that water vapour can be converted to steam quickly even when it is warm. They are also cooler so the gases don’t rise and disperse in air. They float at low levels.

According to boiler flue position regulations, condensing boiler flues should therefore be placed 2.5m away from any adjacent buildings, walls, fences, or boundaries.

Distance to the neighbor’s house

You don’t want harmful gases from your home to be emitted into the homes of your neighbors. A boiler flue must be installed at least 600mm from a wall, fence, or other building.

The minimum distance required for flue installation is 600 mm from a wall, building, or fence that is facing the boundary. However, the flue should be installed in the backyard. This will reduce the risk of causing “Statutory Nuisance.”

Distance to an open window

A boiler flue’s purpose is to remove toxic gases from the house. The boiler flue regulations require that the flue be placed at a safe distance to any openings in the house including windows and doors. The distance depends on the size of your boiler. The boiler size determines the distance. It is typically between 30cm-60cm to the side, either above or below the door or window.

This regulation prevents harmful gases from entering your home.

Condensing boilers & height flue kits

If you live in an area where the horizontal flue is too close to public property, you should call a boiler engineer to have it reinstalled. To allow toxic waste gases to escape, the flue must be installed at least 2.1m above the ground according to flue regulations.

Other boiler flue regulations

Boiler installation engineers must follow the following existing boiler flue installation regulations to prevent harmful gases in your home.

  • The flue should always be sealed on both ends. A gas safe engineer will seal the gap through the wall using caulk, cement or other industry sealants. The sealing of a home ensures that no gas escapes or re-enters it.
  • If you’re changing from a non condensing boiler to one with condensing heat, the angle must be correct. A bad angle can cause some drips to escape.
  • Secure joints with screws – brackets, pipework, extensions, and other fittings must all be properly fixed. If the joints are not secured properly, they can become dangerously loose over time.
  • It is important that all parties are aware of the flue length. When adding bends or extensions to flues, it is necessary to know how long they will be. A 45-degree bend, for example, adds an additional meter to flue length.

You should also be aware that too many bends or extensions can cause the flue to become too long and make it difficult for gases to escape. This will cause the boiler to lose efficiency. The boiler and boiler manufacturers’ guidelines will determine the maximum flue length.

The Viessmann Vitodens 050-W 29kw has a maximum flue length of 15m, while the 35kw version has a maximum length of 20m. It all boils down to safety and health, but different manufacturers use different criteria to determine the maximum length.

Should my boiler be moved because of an incorrect flue?

If your existing boiler flue is not in compliance with the above boiler flue position regulations (e.g. it is located below the recommended height facing a public area), then you will need to install a new boiler.

Most boiler flue regulations only apply to new boiler installations. Before you spend a lot of money on boiler flue regulations, consult a Gas Safe registered engineer.

All new boiler installations must be equipped with condensing boilers in accordance with UK regulations. Condensing boilers have higher efficiency. Two internal heat exchangers make them more efficient.

They lose less heat through the flue pipe. You will need to relocate the flue to comply with the condensing boiler flue regulations when you replace your noncondensing heating boiler.

Moving the boiler

You might need to move your boiler to another room if you want to make it look more attractive or free up space in the existing room.

The boiler flue regulations can be met by moving the flue with the boiler. Moving a boiler costs between £250 to £600 on average. Extra costs can be incurred if the flue must be extended or moved. If you want to change to a vertical flue terminal, expect even higher costs.

Do you need planning permission to install a new boiler flue in my home?

Planning permission is not required if the boiler flue that you install meets current boiler flue regulations. If the boiler flue is not in compliance with the regulations, planning permission will be required. A gas safe engineer can help you ensure that your boiler flue is installed in accordance with the boiler regulations.

Do you need an engineer?

Yes. A registered engineer and Gas Safe heating engineer should be able to assist you in any modifications to the boiler’s setup and flue positioning. If anything goes wrong, the results can be very dangerous and costly.

Gas Safe registered engineers are trained and qualified to perform flue repositioning and other related tasks on various boiler types, brands, and models. Never use a heating engineer who isn’t on the gas safe register.

Getting a new boiler and following the boiler flue guidelines

Whether it’s combi boilers, system boilers, or regular gas boilers, it is essential that you are familiar with boiler flue regulations. You should be familiar with boiler flue regulations if you need to have a boiler repositioned or serviced. Look it up if you can. Any new boiler installation should only take place if all these regs can be adhered to.

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