Still thinking of upgrading your heating system? This back boiler to combi conversion guide is exactly what you have been waiting for. Back boilers were once common in UK homes, typically hidden behind gas fires and serving both central heating and hot water needs. However, modern combi boilers are now the preferred choice due to their energy efficiency, space-saving design, and better performance.
This article will talk you through everything you need to know in converting from a back boiler to a combi boiler, including costs, steps, benefits, and what to expect.
Why Convert from a Back Boiler?
Before diving into the steps, let’s briefly explore why homeowners are switching from back boilers to combi systems:
Efficiency: Back boilers are generally rated at 65-70% efficiency, while new combi boilers can exceed 90%.
Space Saving: Combi boilers don’t need water tanks or hot water cylinders.
Modern Controls: Smart thermostats and controls integrate easily with combi boilers.
Compliance: Back boilers no longer meet current Building Regulations for energy performance.
If your back boiler is old, noisy, or unreliable, it might be time to upgrade.
Step-by-Step Back Boiler to Combi Conversion Guide
Converting from a back boiler to a combi boiler is not a simple swap; it’s a full heating system upgrade. Here’s what the process typically involves:
1. Survey and Assessment
A Gas Safe registered engineer will inspect your home to:
- Assess current pipework
- Check flue placement and access
- Decide on new boiler location
- Plan cylinder and tank removal
2. Choosing the Right Combi Boiler
Factors to consider:
- Property size
- Number of bathrooms
- Water pressure
- Energy efficiency ratings
Popular brands like Worcester Bosch, Vaillant, and Ideal offer reliable combi options.
3. Removal of the Back Boiler
The existing back boiler (usually behind the fireplace) must be carefully removed. This step often includes
- Disconnecting the gas supply
- Removing the firefront
- Making good the fireplace and chimney
4. Installation of the Combi Boiler
Combi boilers are often installed in the kitchen, airing cupboard, or loft. The installation includes:
- New pipework for gas, water, and central heating
- Fitting a new flue to comply with current regulations.
- Connecting thermostats and controls
5. System Flush and Commissioning
Once the combi is installed, the engineer will:
- Power flush the system to remove sludge
- Test for gas leaks and water pressure
- Program heating schedules
6. Certification and Handover
Your installer should provide:
- Building Regulations Compliance Certificate
- Boiler warranty
- User instructions
How Much Does It Cost?
A back boiler to combi conversion can cost between £3,000 and £5,000, depending on;
- Complexity of the job
- Boiler brand and model
- Amount of pipework rerouting
- Waste disposal and remedial works
Always get at least 3 quotes and make sure the installer is Gas Safe registered.
Benefits of a Combi Boiler
Here’s what you’ll enjoy post-conversion:
- Instant hot water – no need to wait for a tank to heat up
- Lower energy bills due to higher efficiency
- More space with no tanks in loft or airing cupboard
- Quieter, more modern heating system
Government Ban on Back Boilers
Back boilers are now largely phased out and banned under UK building regulations. Due to their inefficiency, safety concerns, and carbon footprint, the government no longer allows the installation of new back boilers in domestic homes.
As part of the UK’s ongoing push for net zero carbon emissions, homeowners are being encouraged to upgrade to more energy-efficient systems like combi boilers through government-backed initiatives.
Access a Free Boiler Replacement via ECO4 Scheme
The ECO4 scheme (Energy Company Obligation phase 4) is the latest government-backed initiative designed to help low-income or vulnerable households switch to more energy-efficient heating.
Who Qualifies?
You may be eligible for a free boiler replacement under ECO4 if:
- Your current boiler is inefficient or broken (including back boilers)
- You receive qualifying benefits (e.g., Universal Credit, Pension Credit)
- Your home has a low Energy Performance Certificate (EPC) rating
- You’re a homeowner or private tenant with permission from the landlord
What You Can Get
- Free boiler upgrade (back boiler to combi conversion included)
- Home insulation (loft, wall, floor)
- Heating controls (smart thermostats, TRVs)
Take Action Now
If you’re still relying on a back boiler, the time to act is now. Back boilers are obsolete, and upgrading to a modern combi boiler could drastically improve your energy efficiency and lower your bills.
Check if you’re eligible for a free boiler under ECO4 and say goodbye to outdated heating systems. Fill the form here
Frequently Asked Questions
Q: Can I convert a back boiler myself?
A: No. Only a certified Gas Safe engineer can legally carry out this work.
Q: How long does the conversion take?
A: Typically 2–4 days, depending on the complexity of removal and installation.
Q: Will I need to redecorate?
A: Possibly. Fireplaces and walls may need repair or plastering after removal.
This back boiler to combi conversion guide should give you a clear understanding of the upgrade. While the initial cost may seem high, the long-term savings, improved efficiency, and modern features make it worthwhile for most UK homeowners.
Don’t forget to check your eligibility for a heating upgrade. Limited funds available. Click here to confirm if you are eligible.