Boiler flues

A Comprehensive Guide For Your Boiler Flues

Sep-2020 / 6 min read

Reading Time: 6 minutes

Every part of your central heating system is essential, from the boiler down to your flues. Everything works together to heat your home safely. For the most part, that means maintaining your current boiler and bleeding your radiator at least once a year. But what about your flues? 

Boiler flues are the unsung heroes of your heating system, and they should be given the same amount of consideration as you do with your boiler. After all, whether you rent a flat or own a house, it is important to learn about how different parts work. When you have a good idea about their role in the overall system, you can better care for your home, and in turn, it will take better care of you. 

What Is A Boiler Flue?

While your boiler works hard to keep your house warm, your flues work to keep it safe for you to live in. They act as the exhaust pipe of your home. It connects your boiler to the outside and is the pathway for your heating by-products like air, gas, and condensation. 

While these things are not particularly harmful in small doses, they can easily build up and become a health hazard. Condensation can lead to mould and combustion by-products to carbon monoxide poisoning, among many others. With your flues and proper ventilation, you can keep your place safe and warm.

How Do They Work?

In most fuel-burning models, like a gas boiler or oil boiler, you get your heat from combustion. This process creates waste gas, and too much of it can negatively affect your health. Your boiler flue runs from the combustion chamber to the nearest external wall to properly expel the fumes according to the rules and regulations. It travels through the pipes with the help of a fan to the boiler flue terminal. This terminal takes care of releasing exhaust gases and water vapour while also allowing fresh air to enter. 

However, for modern condensing boilers, this process is different. Your flue has a more integral role in heating your home. Instead of quickly expelling the gas, it first passes through the heat exchanger. It goes through the chamber where cold water re-enters the boiler and partially heats it before leaving the house. The cooled water vapour becomes condensate and has a separate drain, while the rest of the gases exit through the boiler flue terminal. Since the flue gases pass a bit of the heat back, condensing boilers are more efficient. 

Find the best local plumbers in the UK!

More info here!

How Much Would It Take To Install A Proper Flue?

It is difficult to give a proper average for the cost of installing a boiler flue because every person’s set up can be unique. Besides considering the house’s shape and structure, you also have to think about the placement of the flue terminal. In crowded neighbourhoods, you need to make sure that people in the surrounding area, including passersby, are not affected by the released gas and air. Your flue system has so many variations like having a square or rounded flue pipe or a horizontal or vertical flue. 

For a regular, horizontal flue kit, you can find one within the £36-£150 range. Vertical flue kits are not that different but are considered more expensive because of the changes in the scaffolding and tiling. It usually has more parts to accommodate your pitches or flat roof. Even without accounting for labour, you can add £100-£200

Besides the main pipe and terminal, there are other accessories like a flue guard, which retails from £12 to £25, and a boiler plume kit, which can range from £75 to £150. If you are installing your flue for the first time, the total price could go from £200 to £350

When you already have one in place and are looking to redirect it, the job should cost around £250-£300. Flue systems involve a lot of other trade work with opening walls and ceilings. So it isn’t unheard of to have a £900 bill for major upgrades, given the labour and material costs. 

As tempting as it is to DIY your installation, it can only be done by Gas Safe registered companies to ensure that everything is secure. You can call us here at Plumbingforce for a local heating engineer. If you want a more exact quote, you can submit a risk-free enquiry, and we will get back to you as soon as possible.

 *Note that the prices shown are just estimates. There are several factors that may affect your total bill. Discuss the actual price with your plumber before proceeding with any construction.

Important Things To Take Note 

Not All Boilers Have Flues

While most boilers have flues, it is possible not to have one. Traditional back boilers have an open system and are the only type of boiler that does not have flues. While it might seem like an appealing option, they are tightly regulated and can be very dangerous when they are not handled properly. They are very inefficient, and there is a nationwide movement for more sustainable options like a condensing boiler or combi boiler. 

Flue Shapes And Sizes

If you are repairing/ replacing your flue pipes, remember that there is no one-size-fits-all kit. Older homes tend to have a square flue with 15 mm pipes. When this is the case, chances are your system is not up to code, and it can be difficult to replace parts without having them custom-made. There have been many changes with the rules and regulations. Unless you have a listed home, you should look into upgrading your system. If you have a more recent building, you can work with the regular 22 mm round flue.

Flue Inspection Hatch

Besides figuring out where to position your flue, you should also consider how to make them accessible. Most homes in the UK have an inspection hatch that allows Gas Safe registered engineers to inspect and maintain your system properly. When your boiler flue is acting out, they should be able to easily diagnose the problem. 

Where Can I Find My Boiler Flue?

Your boiler flue usually takes the shortest and straightest route to the outside. It is located behind the boiler and exits through the nearest external wall. However, since homes vary, there is no fixed place. Most homes keep their boilers in the attic or loft, but you can also find them in basements and small closets. As long as it meets the boiler and flue regulations, you can find your boiler flue just about anywhere. 

If you have a vertical flue, then it comes out from the top of your boiler and exits through the roof. It acts and looks like a chimney, but instead of billowing smoke, you get steam – and lots of it. Given the location of vertical flues, you need to make sure that it is properly sealed. Unlike horizontal flues that get a bit of protection from the wind and rain with neighbouring buildings and roof overhangs, vertical flues are left to the elements. You may need to invest more to protect your flue terminal. 

The Best Location For Your Flue

The best place for your flue is one that meets regulations and serves you for a long time. When you are planning your build, envision the changes that may happen around the neighbourhood. What might be an excellent location for your boiler flue terminal might be an issue when the building next door is completed. You may be forced to add a plume deflector to redirect the air and gas away from the now busy area. When you manage to find a location that ticks off both boxes, you save yourself from the hassle. 

When in doubt about where to put your boiler flue, it is always best to consult an engineer and bring up your concerns. They can inspect your property and come up with the most satisfying solution. For new boiler installations, you can contact us here at Plumbingforce!

What Are The Boiler Flue Regulations? 

Even with the professionals on the case, it wouldn’t hurt to be aware of the boiler flue regulations. Here is a brief rundown: 

  1. When the flue terminal is towards a frequently used pathway, it should be 2.1 m above ground level.
  2. When it is near a window or air vent, it should be 300 mm away (either above, below or beside the opening). 
  3. It should be 75 mm below guttering and drain pipes.
  4. It should be 200 mm below the eaves/roof overhangs. 
  5. For vertical flues, it should be 2 m below roof windows/skylights.
  6. For vertical flues, it should also be 300 mm above the roof pitch or flat roof. 

When you have your flues installed, you should make sure the area is clear. Most boilers are kept in rooms filled with other items. If this is the case for you, leave a little bit of leeway between your heating system and other items. 

Connect with the best local plumbers and boiler engineers near you

The Importance Of Your Boiler Flue and Proper Ventilation

Your boiler flue and ventilation system keeps your gas appliances working safely and efficiently. It keeps a decent fresh air supply for proper combustion and gets rid of waste gases. The one you should keep an eye out for is carbon monoxide.

Carbon monoxide is a colourless and odourless gas. Many consider it a silent killer because its effects are gradual and symptoms are often associated with other ailments. When you get headaches and feel nauseated, is it carbon monoxide poisoning or a stressful week? 

To avoid CO poisoning, you should have proper gas safety measures in place. Besides working closely with your gas engineer and keeping your boiler and flues in tip-top shape, you can also look into CO detectors to round out your system. With this in place, you can prevent the worst from happening. 

Our home is meant to be a safe space to rest and recharge. It should never be a health and safety hazard. While you don’t see your flue system, they are an integral part of your home’s heating and ventilation. 

For any heating issue, you can book our services online or call us at 0330 162 5329. We handle regular boiler maintenance and installations along with same day emergency repairs. When you need immediate service, Plumbingforce is more than ready to address your needs.

Before You Go...

Sign up to our newsletter and enter our prize draw for a chance to win a new boiler system up to the value of £500!