Boiler Installation

There is no single best boiler; there is the right type for your home and how you use hot water.

A combi saves space, but it can only supply a limited flow at once, so two showers running together will both suffer. A system boiler stores hot water ready to use. An unvented cylinder must be installed by someone qualified to fit one under the building regulations.

Before recommending a combi boiler installation, we measure the mains pressure and flow. If the supply is weak, a combi will disappoint whatever its size.

Boiler size means its output in kilowatts (kW), and the right figure is worked out, not guessed:

• Combi boilers are sized mainly by hot water demand. A higher output gives a faster flow of hot water, but only if the mains supply can deliver it.
• System and regular boilers are sized by the heat loss of the home: the size and number of rooms, insulation, windows and walls. The cylinder is sized for the number of people and bathrooms.
• Bigger is not better.: An oversized boiler switches on and off frequently (short cycling), which wastes fuel and wears parts.

We work out the heat loss at the survey. Where rooms need more heat, our radiator installation and replacement service can upgrade them.

• Regular or system boiler to combi: The cylinder, loft tanks and their pipework are removed, freeing up the airing cupboard and loft. The gas supply pipe often needs upsizing to meet a combi's demand, which is part of our gas plumbing service.
• Back boiler removal: An old back boiler behind a gas fire is disconnected and removed, the fire is dealt with, and a new boiler is fitted in a better position.
• Moving a boiler: To a kitchen, utility room, loft or garage, with new gas, water and condensate pipework and a new flue position. A loft boiler typically needs safe, permanent access, boarding and lighting for servicing.
• New spaces: Boilers for house extensions, loft conversions and new builds, planned with the building work.

If you are replacing the whole system, including pipework and radiators, or considering a heat pump, see our central heating system installation service.

The flue terminal must sit set distances from opening windows, doors, air bricks, corners and boundaries, following the manufacturer's instructions and the British Standard for flues. Where the plume would blow onto a path or a neighbour's window, a plume management kit redirects it. A flue that runs through a ceiling or boxed-in void must have inspection hatches so it can be checked at every service.

Condensing boilers also produce acidic water (condensate), which should drain to an internal waste or soil pipe where possible. An outside run is kept short, typically in a larger pipe and insulated, so it is less likely to freeze.

• Gas Safe: Fitting a gas boiler is carried out by Gas Safe registered engineers, as the law requires.
• Boiler Plus (England): A new gas boiler must have an ErP efficiency of at least 92% and time and temperature controls, such as a programmer and room thermostat. A combi also needs one extra energy-saving measure: weather or load compensation, a smart thermostat with automation and optimisation, or flue gas heat recovery. Our thermostat and heating control installation service covers the options.
• Building regulations: A new boiler is notifiable work. The installing engineer notifies building control through the Gas Safe Register, and you receive a Building Regulations Compliance Certificate.
• Benchmark checklist: The commissioning checklist in the boiler manual is completed and signed at installation.
• Water treatment: The system is cleaned, a magnetic filter is fitted and inhibitor is added before the boiler is handed over. Heavily sludged systems may need power flushing first.
• Electrics: The boiler needs a fused electrical supply. Any new circuit or spur is certified through one of the routes the building regulations allow, through our domestic electrical installation service.

Manufacturer warranties: most manufacturers offer a warranty when the new boiler is registered with them. The terms are set by the manufacturer and normally require a yearly boiler service.