Combi boiler installation
Hot water on tap, no tank in the loft, one fixed price.
A combi heats your radiators and your hot water from one compact box, straight off the mains. No cylinder, no cold water tank, no waiting for the tank to heat up. Our Gas Safe registered engineers fit combi boilers in homes across Cornwall, Devon, Somerset and Dorset. We look at your home first, then give you a fixed quote so the price you agree is the price you pay.
Is a combi the right boiler for your home?
For most flats, terraces and smaller semis, yes. A combi suits homes with one main bathroom where two people rarely run hot taps at the same time.
It gets harder in bigger houses. A combi only heats water as it flows, so a shower upstairs and a bath filling downstairs will share the same flow rate. If you have two or three bathrooms and a busy morning routine, a system boiler with a hot water cylinder usually works better. Our guide to combi vs system boilers goes through the trade-offs in more detail.
- Good fit: one bathroom, up to around three bedrooms, decent mains water pressure
- Think twice: two or more bathrooms used at once, weak mains flow, or a big family
- Worth knowing: a combi frees up the airing cupboard and the loft tank space
Combi boilers we fit
Images: Worcester Bosch and Vaillant. See Worcester Bosch boilers and Vaillant boilers.
Mains pressure matters more than boiler size
A combi can only deliver hot water as fast as your incoming mains allows. On the survey we measure your water pressure and flow rate at the kitchen tap, because a big boiler on a weak supply still gives you a disappointing shower.
Then we size the boiler to your home, not to the biggest number on the brochure. If you are unsure what output you need, our guide on what size boiler you need explains how it is worked out.
Swapping a combi for a combi
A like-for-like combi swap is the simplest job we do. The pipes are usually in the right place, the flue route is known, and most of the work is lifting the old boiler off and the new one on.
If you are coming from a tank-fed system or an old back boiler, that is a bigger job. We cover those on our combi conversion and back boiler replacement pages.
What affects the price
The boiler itself is only part of the cost. Flue length, whether the gas pipe needs upgrading, how much the system needs cleaning, and which controls you choose all move the number. We explain the typical price ranges on our new boiler cost page.
We do not publish one price for everyone because homes are not all the same. You get a fixed quote after the survey, in writing, before we book the job.
How long does it take to fit a new boiler?
A straight combi boiler installation is usually one day's work. Where the job needs new pipework, a new flue route or a conversion from a regular boiler, allow two to three days.
Most of the time it takes to fit a boiler goes on things you never see. The engineer drains the heating system, takes the existing boiler off the wall and checks the gas supply and pipework. Then the new boiler goes up, followed by the flue, the condensate pipe, refilling and bleeding the radiators, and commissioning with a flue gas analyser. Before we leave, we show you the controls and how to top up the pressure.
Do you need a new boiler, or a repair?
Not every tired boiler needs replacing. If your current boiler is reliable and passes its annual service, a repair may be money better spent.
It is worth looking at a replacement when breakdowns keep coming back, parts are no longer made, or the boiler type no longer suits the house, for example after adding a second bathroom. If you do decide to get a new boiler installed, the survey confirms whether a combi is still the right boiler for you. Our guide on how long a boiler lasts has more on the signs.
Gas, oil and electric combi boilers
Most combis we install run on mains gas. Off the gas grid, oil combi boilers do the same job from an oil tank, and our oil boiler installation page covers those.
Electric boilers, including electric combi boilers, are another option. They are compact and need no flue, but they tend to suit small, well-insulated homes, and what they cost to run depends on your electricity tariff. We will talk you through the options if gas is not available.
What happens, step by step
Tell us about your home
Send a few details through our quote form or give us a call. It takes a couple of minutes.
Survey
An engineer checks your water pressure, gas supply, flue route and where the boiler should sit.
Fixed quote
You get a written price for the whole job. No extras added on the day.
Installation
Most combi swaps are done in a day. Conversions and relocations take longer, and we tell you that up front.
What is included
- Home survey to check pressure, flow rate, gas supply and flue position
- Removal and disposal of your old boiler
- New combi boiler fitted by a Gas Safe registered engineer
- System clean and a magnetic filter to protect the new boiler
- Heating controls set up and explained before we leave
- Building Regulations registration and manufacturer warranty registration
Combi boiler installation FAQs
How long does a combi boiler installation take?
A straight combi swap usually takes one day. If we are moving the boiler, converting from a tank-fed system or running a new flue, allow two or three. We give you the expected time with your quote, so you can plan around it.
Do I need a power flush with a new combi?
Not always. Every new boiler needs a clean system, but a chemical clean and a magnetic filter is often enough. If your radiators have cold spots or the water runs black, a power flush is the better option, and we will say so on the survey.
Will a combi work with low water pressure?
It will work, but the hot water flow will only be as good as your mains. We measure it before quoting. In a few homes the honest answer is that a system boiler and cylinder will give you a better shower, and we would rather tell you that than fit the wrong boiler.
Is there a warranty on a new combi?
Yes. We fit as a manufacturer-approved installer, so extended warranties are available. The length depends on the boiler and the manufacturer, and we confirm it in writing with your quote.
Can I pay monthly?
Finance options are available on new boilers, subject to status. Have a look at our boiler finance page or ask when you book your survey.
Where are combi boilers usually installed?
Often in a kitchen cupboard, utility room, airing cupboard or loft. Wherever it goes, the boiler needs a flue route to outside, a drain for the condensate and room for an engineer to service it. If you want it somewhere else while you are fitting a new boiler, see our boiler relocation page.
Is a combi boiler better than a hot water tank?
It depends how your household uses hot water. A combi heats water on demand and frees up cupboard space, which suits smaller homes. A system or regular boiler with a hot water cylinder copes better when two showers run at once. We look at your bathrooms, mains flow and family size before recommending a boiler type.
How much does a new combi boiler installation cost?
The installation cost depends on the boiler you choose, the flue, any new pipework and the controls. A like-for-like swap is the cheapest route. We list typical UK boiler prices from Which? on our new boiler cost page, and you get a fixed price from us after the survey.
Get a fixed price for your home
Tell us about the job and we will arrange a free survey.