Gas and boiler guides

The safety guides come first

Two guides here are worth reading before you need them:

• The warning signs of an unsafe gas appliance – staining, a lazy yellow flame, condensation, soot, and the symptoms of carbon monoxide exposure that get mistaken for flu.
• Landlord gas safety certificates, explained properly – what a CP12 covers, what it does not, and what the actual legal obligation is.

Carbon monoxide has no smell and no colour. An audible alarm to the current standard, correctly sited, costs very little and is the only thing that will tell you. See carbon monoxide testing.

Start here, depending on what you are dealing with

Choosing and replacing

A boiler replacement is the largest single purchase most households make for their heating, and the quotes vary far more than the boilers do. The variation is usually in what is excluded.

The things that separate quotes, in rough order of how often they are the hidden difference:

1. Whether the gas supply pipe was measured rather than assumed. A new boiler with a higher input on an undersized supply will underperform and can be unsafe. Gas supply and pipe sizing covers the check most quotes skip.
2. Whether the system is being cleaned before a new boiler goes on it, and what is being fitted to keep it clean. Debris from an old system is the fastest way to wreck a new heat exchanger.
3. What Boiler Plus items are included – the regulations require specific measures alongside a new boiler in England, and they are frequently quoted as extras.
4. Whether the flue route is achievable or involves work nobody has priced.
5. Whether the controls are being replaced, and with what.
6. Whether the condensate can drain internally or needs an external run that will freeze.

• Combi, system or regular – matched to the house and how it is used, not to a sales preference.
• What a boiler replacement actually involves – the whole sequence, and where the time goes.
• Moving a boiler – what changes, and what it costs in disruption rather than parts.
• Flue positions and rules – the constraint that decides which boilers are even possible.

Living with one

Most of what goes wrong with a gas boiler is not the boiler. It is the system around it, the controls, or the pressure.

• Boiler pressure explained – a system that loses pressure has a leak or a failing expansion vessel, and topping it up repeatedly hides the fault while it gets worse.
• Understanding fault codes – what the code narrows it to, and what it does not.
• What a service should include – with the tells that it did not happen.
• Boiler warranties – the conditions manufacturers attach, including annual servicing and system cleanliness, and how claims get refused.

See also gas boiler servicing, gas safety checks and heating controls.