Regular boiler
Also called heat-only or conventional. A cylinder plus cold water tanks in the loft.
Best for: Older homes with low mains pressure, or where the pipework is built around it.
Read more →Conversions · Croydon
Combi conversions and back boiler replacement
Swap an old tank-fed system or a back boiler for a modern combi. Lose the cylinder and the loft tanks, gain a cupboard, and get hot water straight from the mains.
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Before and after
What changes when you convert
Left: what many older Croydon homes have now. Right: where you end up. The loft tanks and the cylinder go; one boiler does the lot.
Back boiler
Sits behind a gas fire in the chimney breast. No longer made, and parts are hard to find.
Best for: Nobody, now. Replacing one is a common job in Croydon’s 1930s semis.
Read more →Combi boiler
Heats water on demand, straight from the mains. No hot water cylinder, no tanks in the loft.
Best for: Flats and most 1 to 3 bedroom homes with one bathroom, or two with a larger model.
Read more →Back boilers
Still got a back boiler behind the fire?
Back boilers were fitted into the chimney breasts of thousands of 1930s semis and post-war homes across Croydon, from Shirley and Addiscombe to Coulsdon and New Addington. They sit behind a gas fire, heat a cylinder upstairs, and were built to last. Many have, but they are no longer made, parts are disappearing, and a breakdown often means a conversion in a hurry.
Replacing one usually means moving the heating to a new combi in the kitchen or an upstairs cupboard, removing the cylinder and tanks, and making the fireplace safe. It’s a bigger job than a straight boiler swap, so the quote form asks where you’d like the new boiler to go. If you’re not sure, choose “Not sure” and we'll advise.
A conversion isn't right for every home. If you have two bathrooms in use at once, a system boiler with a new cylinder may serve you better. We'll tell you which.
The work
What a conversion involves
Cylinder and tanks out
The hot water cylinder and the cold water and expansion tanks in the loft are drained, disconnected and taken away.
Pipework re-routed
Hot and cold water are re-piped to run from the mains through the new combi. Redundant pipes are capped or removed.
Gas supply checked
A combi can need more gas than the old boiler. We check the pipe size from the meter and upgrade it if it’s too small.
Mains flow measured
A combi depends on the cold mains. We measure pressure and flow first, so you know what your showers will be like.
New flue position
If the boiler moves, it needs a new flue through an outside wall or the roof, placed to meet the rules on windows, doors and boundaries.
System sealed and cleaned
Converting from an open-vented system raises the pressure in the pipes, so we flush the system and check for weak spots before it goes live.
FAQ
Conversion questions
How long does a combi conversion take?
Usually two days, sometimes three when the boiler is moving rooms or there’s a lot of loft pipework to take out.
Will my old radiators cope with a sealed system?
Most do. A conversion runs the radiators at a higher pressure than an old open-vented system, which can show up a weak valve or a pinhole in an old radiator. We pressure-test the system and tell you about anything that needs attention before we finish.
Is it worth replacing a back boiler that still works?
Back boilers are no longer made, many are 30 or more years old, and parts are increasingly hard to find. Most owners replace them on their own terms rather than wait for a winter breakdown. Removing one also frees up the fireplace.
What happens to the fireplace after a back boiler comes out?
We remove the back boiler and the gas fire in front of it, and cap the gas safely. The opening can then be left, boarded or used for a new fire. If you want a new gas fire fitted, mention it in the quote.
Can I keep my cylinder and still change boiler?
Yes. If your household uses a lot of hot water at once, keeping a cylinder with a new system boiler can be the better option. See our boiler replacement page.
More boiler help
- Boiler installationNew boilers fitted across Croydon
- Combi boilersHot water on demand, no tanks
- Boiler replacementSwap an old or broken boiler
- Boiler repairBreakdowns, leaks, fault codes
- Boiler servicingAnnual service and landlord certificates
- Installation costWhat decides the price
- Emergency repairNo heating or hot water today
- Landlord certificatesAnnual gas safety record (CP12)
- Power flushClear sludge, fix cold radiators
- Moving a boilerNew room, new wall or the loft
Get a price for your conversion
Answer a few quick questions, add a photo if you can, and a Gas Safe engineer will come back to you with a price.