About this page: Plumbing Contractors London is a free enquiry service run by Web Designer Limited (trading as Zoib). We pass enquiries to independent plumbers and heating engineers; we don’t carry out the work, and we can’t guarantee that every enquiry is taken up. Figures below are quoted from the named sources with their dates; they are not our prices. More about this site.
Who can do which heating job
| Job | Who should do it |
|---|---|
| Any work on a gas boiler, gas fire, hob or gas pipework | By law, a Gas Safe registered engineer qualified for that type of work (see the Gas Safe Register FAQs) |
| Oil boiler | An appropriately qualified installer, such as an OFTEC-registered technician |
| Radiators, pipework, valves on a wet system | A competent plumber or heating engineer; if the boiler is touched, Gas Safe applies |
| Unvented hot water cylinder | An installer with the skills for unvented systems, shown for example by competent person scheme registration (see below) |
| Electric underfloor heating, new circuits, wiring for controls | A registered electrician if the work is notifiable under Part P |
The GOV.UK competent person scheme list names the schemes for installing a heating or hot water system or its controls: APHC, BESCA, Blue Flame Certification, Gas Safe Register, Certsure, HETAS, NAPIT and OFTEC. A registered installer can self-certify the work instead of you applying to building control.
Boiler replacement: published 2026 costs
We don’t price heating work. These figures are from Checkatrade’s new boiler cost guide (table last updated October 2026):
| What | Published figure |
|---|---|
| Like-for-like combi replacement, same location (supply and install) | Usually £2,500 – £4,000 |
| Gas combi, average total | About £3,000 |
| Regular or system boiler converted to a combi | Around £4,000 |
| Installation labour | £1,000 – £2,000 |
| Moving the boiler (labour) | Around £1,000 |
| Powerflush | Around £1,000 including VAT |
| Magnetic filter | £60 – £160 supply, plus £50 – £150 to fit |
| Typical time | 4–6 hours like-for-like; 1.5–2 days for a regular-to-combi conversion |
Checkatrade says labour costs are typically higher in London and the South East than elsewhere. It also notes that the Boiler Upgrade Scheme in England and Wales supports eligible heat pumps and biomass boilers, not replacement gas boilers.
Unvented hot water cylinders
Many London homes swap a tank in the loft for a mains-pressure unvented cylinder. Approved Document G (paragraphs 3.40 to 3.42) says the safety of an unvented system depends on choosing the right system and safety devices and installing them correctly, so you should choose installers with the necessary skills. Installing an unvented system is notifiable building work. If the installer is registered with a competent person scheme for unvented systems, they can self-certify, and you should receive a Building Regulations compliance certificate. Otherwise building control must be notified before work starts.
Underfloor heating
- Wet systems run warm water through pipes in the floor from a boiler or heat pump, via a manifold. They suit extensions and ground floors being dug out or relaid. Ask about floor build-up height, controls and how the system is balanced with your radiators.
- Electric mats are common in bathrooms. In the zone around a bath or shower, Approved Document P makes adding to or altering a circuit notifiable, so use a registered electrician who will certify it.
Certificates to keep
- A Building Regulations compliance certificate for a new boiler, cylinder or other notifiable heating work.
- The boiler’s commissioning checklist and the manufacturer’s warranty registration. Checkatrade notes you may need annual servicing to keep a boiler warranty valid.
- Electrical certificates for any new circuits or electric underfloor heating.
Landlords: annual gas safety checks
If you let a property with gas appliances, the Health and Safety Executive’s guidance for landlords sets out your duties, including an annual gas safety check by a Gas Safe registered engineer and giving tenants a copy of the record.
If you would like us to pass a heating enquiry to an independent plumber or heating engineer who covers your area, use the enquiry form. For anything urgent, see emergency plumbing: what to do first. We don’t carry out the work ourselves.
Questions people ask
Can any plumber replace my gas boiler?
No. By law, anyone working on gas appliances must be on the Gas Safe Register, and qualified for that type of work. The back of the engineer’s Gas Safe ID card lists their qualifications, for example “Gas Boiler”.
How much does a new boiler cost in London?
Checkatrade’s 2026 guide says a like-for-like combi replacement usually costs about £2,500 to £4,000 supplied and fitted across the UK, and that labour is typically higher in London and the South East. Changing boiler type or moving the boiler costs more.
Is installing an unvented cylinder notifiable?
Yes. Approved Document G says installing an unvented hot water system is notifiable building work. An installer registered with a competent person scheme for unvented systems can self-certify it; otherwise building control must be told before work starts.
Can underfloor heating run off my existing boiler?
Often, a wet underfloor system can be connected to an existing boiler through a manifold and suitable controls, but it depends on the boiler, the system and the floor. Ask the installer to explain the design and controls in writing.
Sources
- Gas Safe Register – frequently asked questions
- Gas Safe Register – the Gas Safe ID card
- GOV.UK – Competent person schemes
- Checkatrade – How much does a new boiler cost in the UK in 2026?
- GOV.UK – Approved Document G (paragraphs 3.40–3.42)
- GOV.UK – Approved Document P: electrical safety
- HSE – Gas safety: landlords
Sources checked on 20 October 2026. General information only, not legal, planning, structural or financial advice.
Related pages
- Emergency plumber in London
Gas smell, burst pipe or leak? What to do first, who is responsible for which pipe, and how to check an emergency plumber.