G3 competence, notification and certification

Core idea

An unvented hot-water store contains heated water under pressure, so Approved Document G requires appropriate competence and safety provisions. Installing a new unvented hot-water storage vessel with a capacity greater than 15 litres is notifiable building work in England. The installer’s technical competence and the administrative route used to notify or certify the work are connected but separate questions.

What to recognise

• Use a suitably competent installer for the unvented system and its safety controls.
• A member of an applicable competent person scheme may self-certify work within that scheme.
• Otherwise make the required application or notice to building control before or as required for the work.
• Commission and leave the safety devices, discharge routes and documentation complete.
• Keep evidence of notification or certification with the installation records.

Apply it

Before work starts, identify who will design and install the system, who is registered to self-certify, and which building-control route applies. Do not discover at handover that the installer is competent but has no certification route. Verify the actual scheme scope rather than assuming any trade membership is enough.

Keep the boundary clear

This note describes the England Approved Document G route; other UK jurisdictions differ. Scheme membership does not replace sound installation, and technical competence alone does not grant self-certification. Alterations affecting safety devices or discharge pipework remain safety-critical work.

The small-vessel notification exception

A hot-water storage system with a vessel of 15 litres or less can be exempt from notification under Schedule 4 when any associated electrical installation work is also non-notifiable. This is a notification exemption, not an exemption from the applicable safety requirements. Check the complete work and jurisdiction before choosing a route.