Yes. A new unvented hot water cylinder is notifiable building work in England under Requirement G3 of the Building Regulations 2010. It needs its own sign-off and is not covered by the boiler's certificate. Where the installer is registered with a competent person scheme for unvented hot water systems, no advance notice to building control is required. Without that registration, the work must be notified to a building control body before it starts. This page also covers the other work carried out on the same day that carries its own notification.
Does a new unvented cylinder need building regulations notification?
Yes. Installing an unvented hot water cylinder is building work in England under Requirement G3 of Schedule 1 to the Building Regulations 2010. Approved Document G treats it as a hot water safety matter. An unvented cylinder is one fed straight off the mains, with no cold tank in the loft.
Two lawful routes lead to the same sign-off. Where the person fitting the cylinder is registered with a competent person scheme for unvented hot water systems, no advance notice to the building control body is required. Where nobody holds that registration, the work has to be notified to a building control body before it starts.
Gas registration does not cover this work, and neither does a general heating registration. The scheme entry has to name unvented hot water storage. Our guide on who can install an unvented hot water cylinder explains the competence this work needs.
Is the unvented cylinder covered by the boiler's building regulations certificate?
No. Schedule 3 to the Building Regulations 2010 lists work types separately, and installing a heating or hot water system is a different entry from unvented hot water storage. A compliance certificate names the work that was certified. If the cylinder is not named on the boiler's certificate, it has not been signed off.
Expect two documents after a same-day job. One covers the boiler and heating work, one covers the unvented hot water system. The manufacturer's Benchmark checklist is a third thing again: Baxi and Ideal Heating describe it as the installation and commissioning record handed to you, not as the building regulations certificate. What the cylinder paperwork should say is set out in our guide to the unvented hot water cylinder certificate.
Ask for the cylinder's certificate by name: a building regulations compliance certificate for unvented hot water storage. The boiler certificate, the Benchmark checklist and a gas safety record are three different papers, and none of them replaces it.
Competent person scheme or a building control application: the two notification routes for an unvented cylinder
An unvented cylinder in England can be signed off through a registered installer's scheme or through a building control body. The route decides when the notification happens and who issues your certificate.
| What differs | Installer registered for unvented hot water | Notified to a building control body |
|---|---|---|
| Before work starts | No advance notice to the building control body is required, because Approved Document G accepts scheme registration as proof of competence. | The work must be notified to a building control body before it begins. |
| Who confirms compliance | The person carrying out the work self-certifies it under Regulation 20 of the Building Regulations 2010. | The building control body deals with the application and issues its own paperwork. |
| What reaches you | A building regulations compliance certificate for unvented hot water, carrying the scheme notification number. | Completion paperwork from the council or from a registered building control approver. |
| Deadline set in law | Regulation 20 requires the certificate or notice to reach you and the local authority no later than 30 days after the work is finished. | Timing follows the application and inspection process of the body you applied to. |
| Who may use the route | Only a person registered with a scheme listed in Schedule 3 for unvented hot water storage systems. | Open to any installation, including work by someone without that registration. |
Either route ends in a record you keep with the house. GOV.UK points out that without building regulations approval you lack the evidence of compliance that is asked for when a property changes hands.
Which other work alongside the boiler and cylinder needs its own notification?
Each type of notifiable work carries its own sign-off, even when it all happens in one day. GOV.UK lists installing or replacing a heating system, and adding radiators to an existing system, among the work that needs building regulations approval in England. The items below are notified or recorded separately from the unvented cylinder.
- Boiler or heating system replacement. Notified as heating work. Approved Document L for dwellings also sets requirements for heating controls and for commissioning when a heat generator is replaced.
- Extra radiators. GOV.UK names adding radiators to a heating system as work that needs approval.
- A new or extended flue. Approved Document J requires a permanent notice plate in the building, giving the flue location, its category, the appliance types it suits and the installation date. Flue work is for a Gas Safe registered engineer.
- Commissioning of fixed building services. Regulation 44 requires a commissioning notice to the building control body, and no later than 30 days after completion.
- Electrical work in the home. Approved Document P makes a new circuit, a consumer unit replacement, and changes to circuits in a room with a bath or shower notifiable. We do not carry out electrical work, so that part is certified by a registered electrician.
Does the water supplier have to be told about an unvented cylinder as well?
Yes, and that notice has nothing to do with building control. The Water Supply (Water Fittings) Regulations 1999 require notice to the water undertaker before certain fittings are installed, and work must not begin without its consent. Consent counts as given if the undertaker does not reply within ten working days.
An unvented water heater holding more than 15 litres is named in those requirements, so a domestic unvented cylinder falls inside them. Two duties therefore run in parallel for the same cylinder. One is the G3 notification through a scheme or a building control body. The other is the water fittings notice to your supplier.
Is a G3 qualification the same as being Gas Safe registered?
No. Unvented hot water competence and gas competence are separate, and gas work is not a building regulations matter at all. In England the Gas Safety (Installation and Use) Regulations 1998 as amended apply. Regulation 3 says nobody may work on a gas fitting unless competent, and businesses must belong to a class of persons approved by HSE.
HSE states that work on gas fittings in homes must be carried out by a Gas Safe registered engineer who is qualified for that particular work. An engineer may hold both the gas registration and the unvented hot water registration. Where a boiler and a cylinder change together, ask to see both. FM Power is Gas Safe registered.
What if the unvented cylinder was never notified to building control?
Missing notification for an unvented cylinder usually surfaces at sale or remortgage. GOV.UK warns that without building regulations approval you will not have the evidence of compliance that is asked for when the property changes hands. A buyer's solicitor looks for the certificate that names the hot water work, not just the boiler.
Check what you already hold before assuming the worst. The compliance certificate shows the address, the date and the work certified; a Benchmark checklist on its own is not that document. Past work that was never notified is dealt with after the event through a building control body, and our guide on a boiler not notified to building control explains how that route works.
If you let the property, the gas appliances also need their annual check, and you can arrange a landlord gas safety certificate while the cylinder work is being planned.
Sources
- Approved Document G: sanitation, hot water safety and water efficiency (2015 edition with 2024 amendments)
- The Building Regulations 2010, Regulation 20 (self-certification and the 30-day rule)
- The Building Regulations 2010, Schedule 3 (self-certification schemes by work type)
- The Building Regulations 2010, Regulation 44 (commissioning notice)
- GOV.UK: Building regulations approval — when you need approval
- Approved Document J: combustion appliances and fuel storage systems (2022)
- Approved Document P: electrical safety, dwellings (2013)
- The Water Supply (Water Fittings) Regulations 1999
- The Gas Safety (Installation and Use) Regulations 1998, regulation 3
- HSE: domestic gas frequently asked questions
- Baxi: Benchmark for installers
- Ideal Heating: Benchmarking