Replacing Your Old Boiler

As of April 1st 2005, a change in the building regulations legislation means that most boilers fitted after this time must be high-efficiency condensing boilers. A high-efficiency condensing boiler is the most efficient boiler type available. It converts more than 88% of the fuel it uses into heat, compared to 72% for conventional boiler types.

High-efficiency condensing boilers are established products and can be fitted to most new and old heating systems. These boilers are so small that they can often be fitted into a kitchen cupboard!

High-efficiency condensing boilers have either a larger or second heat exchanger, which saves the heat that would normally escape up the flue in normal boilers. This reduces the temperature of the flue gases to a point where water vapour produced during combustion is ‘condensed out’. Hence the name ‘high-efficiency condensing boiler’.

If everyone in the UK installed a high-efficiency boiler, we would save enough money to pay the entire annual fuel and power bills of over two million households!

Is your boiler energy efficient?

If it’s 10-15 years old then it probably isn’t. Replacing your old boiler with a new condensing boiler can save you around a third on your heating bills straight away.

Around 60% of CO2 emissions from your home are down to your boiler. With an efficient new boiler you could save up to 875kg of CO2 and £130 a year.

Add in a full set of heating controls as well as a new boiler, and you could increase the total savings to around £250 and 1.7 tonnes of CO2 a year.

Most of us are familiar with the main parts of a central heating system: the boiler, the radiators and the piping that connects it all. The boiler heats the water and this is usually circulated through the pipework and radiators by a pump, before returning to the boiler. From this basic arrangement a number of different systems and boilers have been developed; below you’ll find a guide to the 3 types most commonly found in British homes.

Quick Guide to Boiler Types

  1. Combination (or combi) boilers – heat water instantaneously on opening a hot tap, so there is no need for a storage cylinder.
  2. System boilers – these are designed to generate heat for your home as well as hot water that can be stored in a separate hot water storage cylinder. This can be situated anywhere in your home with no need for a separate tank in the loft.
  3. Heat only boilers – work in conjunction with a hot water storage cylinder and cold water top up tanks to provide both central heating and hot water.

The type of boiler you need will depend on a number of factors, such as the size of your house and your hot water requirements.

1. Combination or ‘combi’ boilers

This is the most popular type of boiler in the UK, now found in around 70% of homes.










Combi boilers provide central heating and hot water without the need for a separate tank to store water; hence you can easily tuck them away under the stairs or in kitchen cabinets.

They are most suited to: Homes with one bathroom, households with single people, couples, families with one child Usually available in following outputs: kw 24 30 35


  • Instant, unlimited domestic hot water
  • Compact, easy to fit if space is limited


  • Unable to run multiple showers or baths at the same time
  • Lower flow rate for hot water than an open vent or system boiler

2. System boilers

A system boiler (sometimes known as a ‘sealed system’) provides central heating and hot water via a storage cylinder housed in an airing cupboard – no need for water tanks in the loft, as with an open vent boiler.

Most suited to: Larger homes with multiple bathrooms/ensuites; families. Usually available in following outputs: kw 12 15 18 24 30 38


  • High flow rate for domestic hot water
  • No tank(s) in your loft
  • More than one hot tap/shower can easily operate at same time


  • Hot water is not instant.
  • Once the water in the storage cylinder runs out you have to wait for it to reheat.
  • You’ll need to find space for the cylinder (usually an airing cupboard).

3. Open Vent Boilers

Open vent boilers are a peculiarly British invention. An open vent (sometimes known as heating only) provide central heating and hot water via a boiler, a storage cylinder housed in the airing cupboard and water tanks in your loft. If you’re looking to do a full system overhaul most people opt to remove the tanks from the loft and turn their open vent system into a sealed system.










Most suited to: Larger homes with an existing open vent boiler. Usually available in following outputs: kw 12 15 18 24 30 38


  • High flow rate for domestic hot water
  • More than one hot tap / shower can easily operate at same time


  • Once the water in the storage cylinder runs out you have to wait for it to reheat.
  • You’ll need to find space for the cylinder (usually an airing cupboard)
  • The bulk feed and expansion tanks are usually sited in the loft – this can create a problem if you’re considering a loft conversion.

No two homes are the same and that’s why we give you a personally tailored energy efficient home heating survey and free quotation based on your current needs.

The total cost for the installation of a boiler or central heating system can differ enormously in price according to the technical specifications of your gas and electrical installation, the size and construction of your property, the number of people living there and so many, many other variables which is why we can only provide an accurate quotation where we guarantee to heat your home efficiently and effectively based on your total needs following a in home survey and full analysis of your current equipment and usage. All our home heating advisors are energy efficiency trained and will not only advise you on the correct choices but will also recommend the most energy efficient way of heating your home.

Step-by-step guide to buying a new boiler from Combiline

  1. Book an appointment
    Call us on 0117 3251111 to arrange an appointment with one of our Heating Advisors, who will provide you with a free no obligation quote.
  2. Your appointment
    Appointments last about an hour, during which our Senior Engineer will carry out an energy assessment of your property and your current heating system. They will then talk you through a detailed quotation and discuss other relevant options.
  3. Confirming the installation
    If you’re happy with our quotation and would like to proceed, we will arrange a convenient time for us to carry out the installation.
  4. Installing your new boiler or central heating
    The highly trained engineers that install your new boiler or central heating are all Gas Safe registered (The Gas Safe register has replaced the CORGI registration scheme). Their work is carried out to the highest safety standards and with minimum disruption to you and your home. Our engineers pride themselves on being friendly and polite – and they always tidy up after themselves.
  5. Completion and handover
    On completion the Heating Installer will explain the use of the new controls and boiler operation. Please make sure you are happy that you know how to use your new system before we leave. We will explain any noticeable differences in the operation between your old and new system, like noise or how long the hot water may take to run through to the hot taps. We will also show you the boiler exhaust and explain how normal operation will produce the ‘pluming’ effect. We will also advise you of the arrangements for the waste to be collected.

Your Heating Installer will treat your property with the most respect and aim to keep any disruption to a minimum. We will cover carpets, protect work surfaces and use dustsheets in all areas where they work. Pleas try to remove furniture, ornaments and other items from the working area around the boiler and radiator positions.

Combiline normally offer boilers from the two leading manufacruers in the UK Market.

With over 40 million units supplied worldwide over the last 125 years, Vaillant Boilers are one of the world’s leading boiler manufacturers. Vaillant have boilers for every type of home and every type of consumer, including industry-leading high efficiency combi boilers that minimise your impact on the environment.




Worcester Boilers are one of the leading British central heating companies with a nationwide network of over 300 service engineers and a comprehensive range of boilers. They are also arguably the field leader in renewable energy products for the domestic market.

All our boilers are fitted with a Magnaclean cleaning filter and room thermostat/programmable room thermostat as standard.



When we visit, we’ll make sure it’s at a time to suit you and our customer service team will phone to tell you when our engineers will arrive. Completing the work on time and ensuring you’re satisfied will always be our priority.


Every one of our engineers is Gas Safe registered and fully qualified to install all types of boilers, including the very latest condensing systems.


All our people are trained to the highest standards of customer service and you can depend on them to clearly explain the work that’s being carried out, why it’s necessary and what the cost will be.


All our parts and labour quotes are guaranteed before your work begins, so you can be sure there’ll be no hidden or extra costs.


We care about your local community and guarantee to install environment-friendly, fuel-efficient systems.