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Boiler Installation and Replacement

A new boiler sized for the house, not the one that was easiest to sell

Combi, system or heat-only. Sized from the property's heat loss and hot water demand, fitted with a system clean and a magnetic filter, commissioned properly, registered for the warranty and the old boiler taken away. New boilers for London homes and rental properties.

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ExcellentMany five-star reviews
Boiler Installation and Replacement

What people say the winter after the new boiler went in

Reviews

Excellent

Rated by London homeowners and landlords

  • Boiler repair, flat

    Boiler locked out on a Sunday evening and the flat was freezing by Monday. Explained the fault code over the phone, turned up when they said, had the part on the van. Heating back on the same visit.

    Sarah M.Reviewed on Google

  • New combi boiler

    Got a written quote with the boiler model, the flush and the filter all listed, nothing added later. Two days of work, tidy, and they talked me through the controls before leaving.

    Daniel O.Reviewed on Google

  • Landlord gas certificate

    Needed a CP12 quickly for a tenancy renewal. Booked for the next morning, the tenant said the engineer was polite and quick, and the certificate was in my inbox that afternoon.

    Priya K.Reviewed on Google

  • Blocked kitchen drain

    Kitchen sink had been slow for weeks and then stopped altogether. Cleared it, showed me the fat build-up on the camera, and gave honest advice on stopping it happening again.

    Tom R.Reviewed on Google

  • Radiators cold at the bottom

    Three radiators were cold at the bottom however much I bled them. Power flush took most of a day and the difference is obvious, the whole house heats up far faster now.

    Helen W.Reviewed on Google

  • Leak under the bathroom floor

    Water was coming through the kitchen ceiling and I feared the whole floor coming up. They traced it to one joint on the bath waste and only lifted two boards. Very relieved.

    Marcus L.Reviewed on Google

  • Bathroom refit

    Full bathroom, old one stripped out and a walk-in shower put in. Plumbing, tiling and electrics all handled by the same people, so nothing fell between the gaps. Really pleased.

    Aisha B.Reviewed on Google

  • Annual boiler service

    Straightforward service, no upselling. Checked everything, cleaned the condensate trap, adjusted the pressure and explained what the readings meant. Booked again for next year.

    George P.Reviewed on Google

What the work involves

Replacing a boiler is one of the few heating jobs where the decisions matter more than the labour. The wrong type of boiler in a house with two bathrooms means cold showers. An oversized combi in a small flat short-cycles and wears out. A new boiler dropped onto a sludged-up system chokes in its first year. And a boiler fitted without a flush, a filter and a proper commissioning record has a warranty that is not worth the card it came on.

Dependable Heating replaces boilers the way the manufacturers intend: survey first, size from the numbers, clean the system, fit the boiler and its filter, commission it with a flue gas analyser, set the controls up, register it and hand over the paperwork. It is a couple of days of work in most homes, less for a straight combi swap, and it is quoted in writing with the boiler model named before anything is ordered.

Where the pipework and radiators are also past it, the job becomes a full central heating installation, and where the boiler is fine but the system is dirty, a power flush comes first. The work reaches across the London areas we cover. Gas boilers can only lawfully be fitted by an engineer on the Gas Safe Register, and every installation is held to that.

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01

Combi, system or heat-only: which boiler suits the property

A combi heats water on demand with no cylinder or tank. It suits flats and smaller houses with one bathroom, frees up the airing cupboard and gives mains-pressure hot water. Its limit is flow rate: one shower at a time, and a bath fills at the pace the boiler can heat the water.

A system boiler heats a hot water cylinder, usually an unvented one at mains pressure. It suits houses with two or more bathrooms, or anywhere several people want hot water at once. The expansion vessel and pump are inside the boiler, so no loft tanks.

A heat-only (regular or conventional) boiler works with a cylinder and loft tanks and is the natural like-for-like replacement in older houses with a gravity-fed system, where changing the whole system is not wanted. It is also the right choice where the mains pressure is too poor for an unvented cylinder.

The choice is made from the hot water demand and the property, not from what is on offer that month. You are told the reasoning either way.

02

Sizing: heat loss, hot water and why bigger is not better

A boiler is sized in two directions. For heating, a room-by-room heat loss calculation gives the output the house needs on the coldest day; most London homes need a lot less than the 30 kW boilers that get fitted by default, and an oversized boiler cycles on and off, wastes gas and wears its components. For hot water on a combi, the flow rate is sized from the number of bathrooms and the incoming mains flow, measured at the tap, because a combi can only deliver what the main brings in.

Both calculations are done at the survey and written into the quote, so the boiler model on the paperwork is there for a reason you can see.

03

What a proper installation includes

The quote lists everything the job needs, and it is more than the boiler:

  • Removal and disposal of the old boiler and, where relevant, tanks and cylinder.
  • A chemical clean or power flush of the existing system, depending on its condition.
  • A magnetic system filter on the return, which every manufacturer now requires for the warranty.
  • New flue and terminal, positioned to the regulations, with a plume kit where a neighbour's window is close.
  • A condensate pipe with a proper fall, insulated or run internally so it cannot freeze.
  • Gas supply checked for the boiler's demand and upgraded where the old pipe is too small.
  • Controls: a room thermostat and a programmer as a minimum, with weather compensation or load compensation where the boiler supports it, and thermostatic radiator valves where they are missing.
  • Commissioning with a flue gas analyser, the benchmark checklist completed, and the boiler registered with the manufacturer and notified to building control.

04

Replacing a back boiler, a floor-standing boiler or a warm-air unit

Plenty of London homes still run on a back boiler behind a fireplace, a floor-standing boiler in the kitchen or, on some estates, a warm-air heating unit. Replacing these is a bigger job than a wall-hung swap: the old unit comes out, the flue route changes, the gas run is often extended and the boiler is repositioned to an outside wall or a cupboard. It is planned at the survey, with the new position agreed with you and the making-good included in the quote.

05

Flats, mansion blocks and shared flues

Boiler replacements in flats have their own rules. The flue terminal has to be a set distance from windows, doors and boundaries, which in a tight lightwell can rule out the existing position. Shared flue systems in mansion blocks have to be assessed as a whole before a boiler on them is changed. Freeholders and managing agents often need to approve the flue position and the condensate discharge. All of that is dealt with before the quote is finalised, so the job does not stall on the day.

06

Warranties, registration and the paperwork you keep

Manufacturer warranties on new boilers run for several years and depend on three things: installation by a registered installer, a filter fitted and the system cleaned, and an annual service recorded in the logbook. All three are done and documented. You receive the benchmark logbook with the commissioning readings, the building regulations compliance certificate, the warranty registration and a walkthrough of the controls before the engineer leaves. Annual boiler servicing from then on keeps the warranty valid.

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How a job runs

How a boiler replacement runs

Two visits before the work starts and one after it ends. The middle bit is a day or two of installation.

  1. Reading the job through before the visit

    01

    Survey

    Heat loss and hot water demand measured, the flue and gas run checked, the system condition assessed, the boiler type and position agreed with you.

  2. Checking the plans and paperwork

    02

    Written quote

    The boiler model, the flush, the filter, the controls, the flue, the making-good and the price, itemised. Nothing changes once you accept it.

  3. Engineer drilling a wall for a fixing

    03

    Installation

    Old boiler out, system cleaned, new boiler, flue, filter and controls in. Commissioned with an analyser and the benchmark completed.

  4. A finished boiler and cylinder installation

    04

    Handover

    Controls explained, paperwork handed over, the boiler registered for its warranty and the first annual service date noted.

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Boiler on its last legs? Get a written price for the replacement

Tell us about the property and the current boiler. An engineer arranges the survey and comes back with an itemised quote.

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Where we work

New boilers across London

Combi swaps in converted flats, system boilers and unvented cylinders in family houses, back boiler removals in 1960s terraces. The towns below are covered, and the housing in each shapes how the job is done.

  • London
  • City of Westminster
  • Islington
  • Chelsea
  • Battersea
  • Holloway
  • Brixton
  • Peckham
  • Fulham
  • Archway
  • Shepherds Bush
  • Canary Wharf
  • Stamford Hill
  • Willesden
  • Cricklewood
  • Putney
  • Streatham
  • Stratford
  • Catford
  • Canning Town
  • Acton
  • Wimbledon
  • Tottenham
  • Finchley
  • Leytonstone
  • Walthamstow
  • Mitcham
  • Wembley
  • Beckenham
  • Brent
  • Morden
  • Edmonton
  • Eltham
  • Croydon
  • Barking
  • Ilford
  • Carshalton
  • Enfield Town
  • Chingford
  • Greenford
  • Harrow
  • South Croydon
  • Hounslow
  • Welling
  • Southall
  • Heston
  • Surbiton
  • Sutton
  • Becontree
  • Purley
  • Borehamwood
  • Ewell
  • Bexley
  • Hayes
  • Dagenham
  • Feltham
  • Banstead
  • Cheshunt
  • Esher
  • Romford
  • Dartford
  • Watford
  • Uxbridge
  • Staines
  • Leatherhead
  • Hatfield
  • Redhill
  • St Albans
  • Grays

Jobs that often go with this one

  • Boiler Service

    Boiler Service

    An annual boiler service that checks combustion, gas rate, flue, seals and safety devices, keeps the manufacturer warranty valid and catches faults early.

  • Central Heating Installation

    Central Heating Installation

    Full central heating systems for homes that have none, and rebuilds of tired ones: boiler, pipework, radiators, controls and zoning designed around the property.

  • Power Flushing

    Power Flushing

    Sludge and rust cleared out of radiators, pipework and the boiler heat exchanger with a proper power flush, so cold spots go and the system runs quietly again.

Resources

Guides worth reading before the visit

FAQ

Boiler Installation and Replacement: the questions people ask first

How long does a boiler replacement take?

A straight combi-for-combi swap in the same position is usually one day. A change of position, a conversion from a heat-only system to a combi or a system boiler with a new cylinder is two to three days. The quote states the duration.

Do I need a power flush with a new boiler?

The system needs cleaning before a new boiler goes on; the manufacturers require it. Whether that is a chemical clean or a full power flush depends on how dirty the system is, which is assessed at the survey and explained in the quote.

Can I keep my hot water cylinder and just change the boiler?

Yes. A heat-only or system boiler works with an existing cylinder, and where the cylinder is sound that is often the sensible choice. If the cylinder is old and uninsulated, replacing it at the same time is usually worth doing and is quoted separately.

Will the new boiler go in the same place?

Where the flue position still meets the regulations and the location suits the new boiler, yes. Where it does not, the survey identifies the options and the quote includes any repositioning and making-good.

What controls come with a new boiler?

A room thermostat and programmer at minimum. Where the boiler supports it, compensation controls that modulate the boiler to the weather or the load are recommended because they make a real difference to gas use. Smart controls can be fitted if you want them.

Is the old boiler taken away?

Yes, along with any tanks or cylinder that are being removed, and the packaging from the new one. The quote includes disposal.

Anything not covered here is answered on our contact page, and the longer reads on boilers, radiators and leaks live in our heating resources.

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ExcellentMany five-star reviews

Tell us about the property and the boiler it has now

How many bedrooms and bathrooms, the current boiler make if you know it, and whether there is a cylinder or tanks in the loft. The survey follows.

  • A written price before any work starts
  • Boilers, gas, plumbing, drains and bathrooms under one roof
  • London and the towns around it

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