Short answer: not a gas boiler, and not an oil one either, unless you are registered to do that work. It is not a matter of preference. It is the law, and the reasons behind it are practical.
What the law says
In Great Britain, anyone who installs, repairs or services gas appliances must be on the Gas Safe Register. That rule comes from the Gas Safety (Installation and Use) Regulations 1998. Doing gas work without being registered is a criminal offence, and the penalties include fines and, in serious cases, prison.
Oil boilers are different on paper. There is no law that says an installer must be OFTEC registered. In practice, though, the work still has to meet Building Regulations, and an OFTEC registered engineer can certify that it does. Without that, you will struggle to prove the job was done properly when you come to sell the house.
Electric boilers sit in a third category. There is no gas involved, so Gas Safe does not apply, but the electrical supply, the plumbing and the Building Regulations still do. In England, certain electrical work in the home has to be done by a registered electrician or checked by building control.
What can go wrong
Boilers look like a plumbing job. They are really a combustion job, and combustion is where the risks sit.
- Carbon monoxide. A badly fitted flue or poorly set burner can release carbon monoxide into the house. You cannot see or smell it, and it can kill.
- Gas leaks. One poor joint on a gas pipe is enough.
- Water damage. Pressure relief and condensate pipes that are fitted wrongly can leak or freeze.
- Voided cover. Manufacturer warranties usually depend on installation by a competent, registered engineer. Home insurers can also refuse a claim if the work was not done to standard.
What a registered installer does that you cannot
A registered engineer checks the gas supply and pipe size before the boiler goes on the wall, sets and tests combustion, checks the flue, commissions the system, and tells the local authority about the job through their competent person scheme. You then get a Building Regulations compliance certificate. That paperwork matters. Solicitors ask for it when you sell.
If the boiler is a Worcester Bosch, an accredited installer can also register the guarantee and offer the longer cover that comes with it.
What you can do yourself
There is plenty of useful work you can do around a new boiler without touching the gas or the appliance itself:
- Clear the space and agree the position with your installer before the day.
- Choose and buy the room thermostat or smart controls you want.
- Bleed your radiators afterwards and keep an eye on the boiler pressure.
- Fit a carbon monoxide alarm, whoever installs the boiler.
Check who you are hiring
Ask to see the installer's Gas Safe ID card, and check the number on the Gas Safe Register website. The card lists exactly which types of work they are qualified to do. For oil, ask for their OFTEC registration.
If you are thinking about replacing a boiler, our boiler installation page explains how we run a job from survey to handover. Or get in touch and we will talk it through with no obligation.
