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Boiler Buying Guide

Save up to £310 every year by upgrading to a new A-rated boiler*

Our boiler buying guide can help you find the right replacement boiler or a new boiler to suit your home and central heating system requirements. We'll show you a list of boilers to choose from that will generate enough heat to keep your home at a comfortable temperature and provide enough hot water for the entire household.

Once you have your list of suitable boilers, simply add the one that suits you best to your basket and checkout when you are ready.

What type of gas boiler do you have?

If you are unsure about your current boiler, or would like a suitable alternative, please select "I'm not sure". Learn about boiler types.

What type of hot water storage cylinder do you have in your home?

This can be either an unvented cylinder or an open-vented cylinder. A cylinder can usually be found in an airing cupboard. Learn about cylinder types.

Does your boiler provide you with instant / unlimited hot water?

If you can hear your boiler 'fire up' when using the hot water it is likely you have a combi boiler and do not have a hot water storage cylinder. Learn about boiler types.

Do you have a cold water storage tank in the loft AND is it in use?

It is possible for some homes to have a cold water storage tank in the loft that is no longer in use. Learn about cold water storage tanks.

Is there a pressure gauge on your boiler?

This can be an analogue or digital interface. Your pressure gauge may be at the bottom of your boiler, or behind a panel on the face of the boiler.

Is your boiler located directly behind your fire?

Back boilers are hidden behind a chimney with a fire in front. Learn about back boilers.

How many bedrooms are there in your home?

How many bathrooms are there in your home?

Please count all bathrooms including ensuite bathrooms. Please exclude cloakroom bathrooms.

What type of flue do you need for your boiler?

You will need a new flue for your new boiler. The flue type is determined by where your boiler is installed. Boilers installed in the kitchen will typically have a flue that terminates on an external wall, requiring a horizontal flue. Boilers installed in an airing cupboard upstairs will typically have a flue that terminates on the roof, requiring a vertical flue. See the diagrams below to match your flue type. We recommend that a Gas Safe registered engineer performs a site visit to determine all necessary components. Learn about flue types.

What is most important to you; the boiler warranty, the lowest price available, or the best of both?

The cost of your boiler will vary depending on its lifespan / warranty. Some boilers include a warranty of up to 10 years. Choose the longest warranty available for peace of mind.

Please note - All boilers available from are A-Rated high efficiency condensing boilers.

*Source Energy Saving Trust. For more information please refer to our Saving Money on Heating Bills Infographic.
Combi Boilers

Combi Boilers

A Combi Boiler, or Combination Boiler, is generally considered to be the UK’s most popular type of boiler. A Combi Boiler is a compact and highly efficient unit, which can supply a busy domestic household with all the heating and hot water supplies it will ever need, whilst guaranteeing significant savings on running and installation costs. Hence why many of us prefer to choose the Combi Boiler over all other types of boiler.

Unlike a conventional heating and hot water system, a Combi system does not store domestic hot water. It heats water directly from the cold mains, as you use it. There is no requirement for a hot water cylinder, a tank in the loft, or the connecting pipe work so there is less risk of freezing and flooding. This will not only save space but also reduce hot water costs, which can account for up to 60% of a typical domestic fuel bill. A Combi Boiler also supplies hot water at mains pressure, giving you exhilarating power showering, without the need for a pump.

Combi Boilers are not suitable for larger properties with 3, 4 or more Bathrooms.

It is a legal requirement that all boiler installations are carried out by a Gas Safe registered engineer.

Regular Boilers

Regular Boilers

Regular Boilers, otherwise known as Heat Only Boilers, Conventional Boilers, or Open Vented Boilers are used in a more traditional central heating system. If you are looking to replace an old boiler, then this may be the system that you currently have.

A Regular Boiler works on the basis of ‘heating only’ and requires a separate hot water cylinder, typically located in an airing cupboard. Additional there are two feeder tanks, typically located in the loft area. One of the tanks is for domestic hot water that feeds to the hot water storage cylinder, the second tank is required for the central heating.

Having a regular boiler system means that unlike a Combi Boiler system, the hot water flow rates tend to be higher as the hot water is already stored in the hot water cylinder. This allows the use of several hot water outlets being operated at the same time within the property. Due to the number of components that a Regular Boiler system requires it will use up more space than any other heating system.

It is a legal requirement that all boiler installations are carried out by a Gas Safe registered engineer.

System Boilers

System Boilers

Sealed System Boilers work in a similar manner as Conventional Boilers, where they indirectly heat a separate store of domestic hot water. System boilers are most commonly used for use with Unvented Cylinders. Unvented Cylinders don’t require a separate header tank in the loft, instead they are filled directly from the mains water supply and are completely sealed.

Although similar in many ways, the difference between a Sealed System Boiler and a Conventional Boiler (Regular Boiler) is that the System Boiler incorporates all the of the major components built-in, including an expansion vessel and modulating pump. Generally all components are pre-wired, pre-plumbed and pre-tested for greater reliability, as well as a quicker and neater installation.

It is a legal requirement that all boiler installations are carried out by a Gas Safe registered engineer.

Unvented Cylinders

Suitable for use with System Boilers

An Unvented Cylinder works off the mains pressure water and therefore eliminates the need for a header tank in the loft.

Unvented Cylinders offer higher hot water flow rates and are therefore able to provide higher water pressure for showers and baths etc. An Unvented Cylinder does not require a feeder tank so this frees up valuable space in the loft area and also gives you the option to site the Cylinder anywhere you want, freeing up further space in the airing cupboard.

Unvented Cylinders are generally manufactured out of top quality stainless steel; this ensures long life and durability. Most Unvented Cylinders can also carry a manufacturer’s guarantee of up to 25 years.

Open Vented Cylinders

Suitable for use with Regular Boilers

An Open Vented Cylinder (or Cistern Fed Cylinder) has a header tank that is usually situated within the loft area. The header tank feeds cold water to the cylinder and relies on gravity to pass water to the heating / hot water system. A vented hot water cylinder is normally associated with a conventional heating system.

Vented Cylinders are typically constructed from copper, with the copper varying in thickness measured in grades. To prolong the life of the cylinder For a longer lasting cylinder choose a higher grade with a greater resistance to copper corrosion. A domestic vented copper cylinder is usually Grade 3.

All Cylinders supplied by us at PlumbNation Heating Supplies are compliant with the new Building Regulations, Part L.

Cold Water Storage Tanks

Suitable for use with Regular Boilers

When cold water needs to be stored to supply an indirect system of cold water, or to feed a system of domestic hot water i.e. an open vented cylinder, the water is stored in a cistern, usually located within the roof space. The cold water storage cistern should have a minimum capacity of 100 litres. If the cistern is also to act as a feed cistern for the hot water supply as well as the indirect system of cold water then it should have a minimum capacity of 230 litres. Cold distribution pipes from the storage tank should be connected so that the lowest point of the water outlet is a minimum of 30mm above the base of the cistern. This is to prevent sediment passing into the pipework. Connections of feed pipes to the hot water system should be at least 25mm above the cold distribution pipes. This will minimise the risk of scolding should the cistern run dry.

Feed and Expansion Tanks

The F&E cistern or feed and expansion cistern is smaller than the cold water storage tank. This is used to supply the water to the open vented heating system i.e. the boiler and radiators. The F&E tank allows the expansion of the hot water within the heating system to vent correctly via a vent pipe which is terminated through the cistern lid and into the tank itself.

Cold Water Storage and F&E Tanks

The Supply float valve should be fitted as high as possible to maintain an air gap and prevent back-siphonage. Overflow pipes should have a minimum internal diameter of 19mm and in all cases be greater in size than the supply pipe. To prevent the ingress of insects, a tight fitting lid must be provided. Where a vent pipe passes through the lid, the pipe must be sleeved. Overflow pipes should also incorporate a filter or screen. Finally the whole installation (cisterns and pipework) should be insulated to prevent freezing.

Back Boiler

A Back Boiler is a compact boiler that is fitted at the back of an open fireplace hearth and can be installed behind a Fire, or within the chimney breast. Even though Back Boilers are fairly small in size, a Back Boiler is more than capable of producing enough hot water and central heating for the entire household if installed with an indirect hot water cylinder, this will allow homeowners to use hot water from several taps at once. Back Boilers are a reliable solution and a Back Boiler installation will usually also include a tank for the loft and a cylinder in an airing cupboard.

It is a legal requirement that all boiler installations are carried out by a Gas Safe registered engineer.

Boiler Flues

The flue system is an essential component of your boiler set up. It provides your appliance with adequate oxygen in order for it to operate safely and efficiently, as well as providing an exhaust for the products of combustion to disperse safely away from your property.

Depending on the location of your boiler you will need to consider what type of flue system would be required with space restraints and gas safe regulations in mind.

If your boiler is located on an external wall then you would normally be fine with a standard horizontal flue that comes with a tight flue bend that is fitted directly to the top of the boiler. If space is an issue then you may opt to go for a direct rear flue. In this scenario the flue would be installed directly behind the boiler and wouldn't have the tight bend on the top.

If the boiler is located on an internal wall or centralised in the property then a vertical flue system would normally be used. This system would normally take a vertical route through the loft space and terminate on either a flat or a pitched roof.

If your boiler is situated in such a way that you couldn't terminate the flue through the roof space and the route is met with installation constraints then you may need to take it vertically first but then run it on a horizontal plane whereas it would terminate through an external wall. This set up would require additional flue components.

Always remember to consult a Gas Safe engineer to ensure the correct flue system is used for your boiler.

Gas Safe Register

Gas Safe Register

Gas Safe Register is the official list of gas engineers who are qualified to work safely and legally on gas appliances. Always check your engineer is on the Gas Safe Register.

It is a legal requirement that all boiler installations are carried out by a Gas Safe registered engineer.