Boiler Upgrade in Milton Keynes: Like-for-Like Swap, Combi Conversion or Back Boiler Removal

People in Woburn Sands, Newport Pagnell and Wavendon search for a "boiler upgrade" and mean very different things by it. For one household it is a tired combi that needs replacing. For another it is a house with tanks in the loft that they want gone. For a third it is a gas fire with a boiler behind it that has been there since before they moved in. Those are three different jobs, and the right quote for one is the wrong quote for the other two.

First, the grant that people confuse this with

The government's Boiler Upgrade Scheme sounds like it should help with a new gas boiler. It does not. GOV.UK is clear that it gives grants to replace fossil fuel heating with a heat pump or a biomass boiler, in England and Wales. A new gas boiler, combi or otherwise, is not covered. If a heat pump is what you are weighing up, our gas boiler vs heat pump comparison covers it, grant included. The rest of this article is about upgrading a gas boiler.

Option 1: a like-for-like swap

The simplest upgrade. A combi comes off the wall and a modern combi goes up in the same place, or a system or regular boiler is replaced with the same type, keeping the cylinder and controls layout the house already has.

This suits most homes where the system is basically right and only the boiler is tired: a lot of the 1980s and 1990s houses around Newport Pagnell and on the Wavendon Gate side of the city, for example, where the second or third boiler is now coming to the end. The survey still matters. The flue terminal has to meet the clearances in Approved Document J and the manufacturer's instructions, which are not always met by where the old one sat. The gas pipe from the meter has to be big enough for the new appliance. And a system that has run on hard water for decades usually needs cleaning before a new boiler goes on it.

Like-for-like does not have to mean the same size. Boilers are often oversized for the house they heat, and a household that has added an en-suite may need more hot water than the old combi gave. The survey sizes the new boiler for the house as it is used now.

Option 2: converting to a combi

Many older homes in Woburn Sands, Newport Pagnell and the villages still run an open-vented system: a cold water tank and a small feed and expansion tank in the loft, a hot water cylinder in the airing cupboard, and a regular boiler. Converting to a combi removes all of that. Hot water comes straight off the mains as you use it, the loft is cleared and the airing cupboard becomes a cupboard.

It is a good upgrade for the right house. It is the wrong one for others, and the honest test is simple:

• How many bathrooms get used at once? A combi heats water on demand. One bathroom, fine. Two showers running together, and both will suffer. Our combi vs conventional comparison goes into this.
• What are the mains pressure and flow? A combi can only deliver what the incoming main gives it. We measure both on the survey. If they are poor, a combi will disappoint however good the boiler is.
• Can the old pipework take pressure? An open-vented system runs at very low pressure. A combi turns it into a sealed, pressurised system. Old joints, radiator valves and pipework that never leaked at low pressure sometimes do once the system is pressurised, so we test and expect to replace weak parts rather than hope.

Where a combi does not suit, the better upgrade is often a system boiler with an unvented cylinder. That still clears the loft tanks and gives mains pressure hot water to more than one tap at once. Our combi vs system comparison and the guides to the cold water tank in the loft and hot water cylinder replacement explain the parts involved.

Option 3: removing a back boiler

A back boiler sits in the fireplace behind a gas fire and uses the chimney as its flue. They were fitted in large numbers in homes of the 1960s and 1970s and some are still running in older houses and bungalows across the area. They are usually paired with loft tanks and a cylinder, so the house is an open-vented system as above.

Replacing one is a bigger job than a swap, and worth understanding before you get quotes:

• The new boiler goes somewhere else. A modern boiler is wall mounted with its own flue, so the first question is where: kitchen, utility, airing cupboard or loft. That choice sets the length of the gas, water and condensate runs.
• The fireplace changes. The back boiler and its fire come out. You can have the opening made good, keep a decorative fire, or fit a new gas fire if the chimney suits it. Decide before the quote, because each is a different scope.
• The system usually changes too. Most back boiler removals are also a conversion to a combi or to a system boiler with a cylinder, so everything in option 2 applies.
• Decommissioning properly. The redundant appliance has to be disconnected and capped by a Gas Safe registered engineer, not just switched off and left in place.

Expect a back boiler job to take longer than a day and to involve some making good. It is also the upgrade that changes the house the most: modern controls, a condensing boiler and a fireplace you get to decide about.

What changes the price of a boiler upgrade

We do not publish prices, because an upgrade priced without a survey is a guess. What the number is made of:

• The type of job: a like-for-like swap is the least work; a combi conversion adds tank and cylinder removal and pipework; a back boiler removal adds relocation and fireplace work on top.
• The boiler: make, model, output and warranty length.
• Where it goes: moving the boiler lengthens the gas, water and condensate runs and may need a new flue route.
• The gas supply: whether the pipe from the meter needs upgrading.
• The condition of the system: cleaning, a magnetic filter and inhibitor are standard; a powerflush if the system needs it; replacing weak valves or radiators on a conversion.
• Controls: Approved Document L sets the minimum standard for efficiency and controls on a replacement boiler.
• Making good: old flue holes, the fireplace, boxing in and taking away the old appliance and tanks.

Two quotes that look far apart are often quoting different jobs. Ask each installer which of the three options they have priced and what is included.

What you should get at the end

Gas Safe Register's guidance on new appliance installations lists what should come with the job: a completed Benchmark commissioning checklist, the warranty registered, and the installation notified to the local authority so that you receive a Building Regulations Compliance Certificate. Keep that certificate with the house paperwork. It will be asked for when you sell.

The honest bit

Not every house needs the biggest version of the upgrade. If your system works, a straight swap with a good clean is often the right answer, and converting a busy two-bathroom house to a combi can make day-to-day life worse, not better. The survey is where we tell you which of the three your house actually suits.

Book a survey

We cover Woburn Sands, Newport Pagnell, Wavendon and the rest of Milton Keynes from our base at Grange Farm. Rob or Sam will look at the boiler, the system, the mains pressure and how the house is used, then give you a written quote for the options that suit it. See our boiler installation service or get in touch.

Frequently asked questions

Does the Boiler Upgrade Scheme pay for a new gas boiler?
No. It funds heat pumps and biomass boilers that replace fossil fuel heating. Gas boiler replacements are not eligible.

Can I get rid of the tanks in my loft?
Yes, by converting to a combi or to a system boiler with an unvented cylinder. Which one depends on how many bathrooms are used at once and on your mains pressure and flow.

Can a back boiler be replaced with a combi?
Usually, yes. The new boiler goes on a wall elsewhere with its own flue, the back boiler is decommissioned and removed, and the fireplace is made good or refitted.

Sources

• GOV.UK, Apply for the Boiler Upgrade Scheme
• GOV.UK, Approved Document J: combustion appliances and fuel storage systems
• GOV.UK, Approved Document L: conservation of fuel and power
• Gas Safe Register, New gas appliance installation