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  • Writer's pictureJeff Culkin

Flues in Voids, Gas Regulations

Updated: May 6, 2022

From January the first 2013 existing gas flues in voids require visual inspection from a gas safe registered engineer. No visual access will result in your boiler being shut down and classified as "At Risk" by your gas engineer, until the inspection issue is resolved. If you are affected you could find your boiler shut down during your annual service or when you call a boiler engineer for a breakdown. Gas engineers will be legally obliged to shut down your appliance. The new regulation was retrospective and applies to all existing boilers and flues, regardless of the installation date. In most cases this can be easily resolved.

Most people are not be affected but if your boiler (or other fan flued appliance) has a concealed flue, e.g. in a ceiling, wall or behind some boxing, you will need to ensure it is visible for inspection. This can be done with the installation of inspection hatches, or by making sure panels are removable.

Many gas/heating companies are labeling these as at risk but allowing the owner to leave them on against their advise, this covers the company from liability.

What is a boiler Flue?

The pipes which take away the fumes from your boiler, and provide fresh air for the burner. This usually consists of what looks like one four inch metal pipe from the top of the boiler, (though it's actually two concentric pipes, one for air in, one for fumes out). It can also be a five inch pipe particularly on longer pipe runs. This is typical on boiler brands such as Vaillant, Worcester, Ideal, Potterton, Baxi, Ariston, GlowWorm, Biasi and Vokera.

On some boilers the flue system will consist of two separate plastic pipes, two inches in diameter or more, this is typical on Keston Boilers.

What is a Void?

A void is a space in your property that you cannot access or use. The spaces under and behind kitchen units can be described as voids. In the context of this regulation a void is a space that cannot be seen into for the visual inspection of the flue. It could be in the ceiling or wall, or it could be purpose built boxing to conceal the flue. Previously it would have been common for builder to conceal flues, and conceivable build a void around a flue.

How do I know if I will be affected?

If you can see the whole of your flue pipe other that when it passes though the cross section of a wall then you are not affected. This will be typical of boilers fitted to or near external walls. Should your boiler be fitted somewhere more central in your property then you will need to consider the flue pipe location, if you can see the entire length of the flue pipe to where it terminates then so you can your gas engineer when he/she comes to do a repair, service, or gas safety inspection. If you have any doubt contact a gas safe registered engineer.

If you need any help or clarity you should contact a local gas sage registered engineer.

Advice on installing inspection hatches from Gas Safe;

It is recommended that inspection hatches are at least 300mm x 300mm and wherever possible, be positioned within 1.5meters of any flue joint in the flue system.

Further information is available from Gas Safe and the HSE

The purpose of this page is for information for home owners and landlords, not for technical guidance. Gas engineers are others seeking technical guidance should see the links above.

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