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Unvented Hot Water Storage Vessel Commissioning Record

An Unvented Hot Water Storage Vessel Commissioning Record confirms that an unvented cylinder (such as a Megaflo, Heatrae Sadia, or OSO) has been installed and commissioned by a G3-qualified installer in accordance with Building Regulations Approved Document G3. It records all safety device checks, discharge pipework compliance, and commissioning measurements.

Building Regulations Approved Document G3, BS EN 12897Valid: One-off (per installation)

What it covers

  • Cylinder specification (make, model, capacity, type)
  • Safety devices (T&P valve, tundish, discharge pipework)
  • Expansion vessel and pressure reducing valve
  • Temperature controls and thermostat settings
  • Cold water supply and hot water performance measurements
  • Compliance with G3 discharge pipe requirements

Who needs a Unvented Cylinder Certificate?

Homeowners
Landlords
Building Control

Create your Unvented Cylinder Certificate with CertBox

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Frequently asked questions about Unvented Cylinder Certificate

Do I need a G3 qualification to install an unvented cylinder?
Yes. Building Regulations require that unvented hot water storage vessels over 15 litres must be installed by a person who holds a current G3 qualification (or equivalent, such as a manufacturer-specific course).
Does the installation need to be notified to Building Control?
Yes, unless you are registered with a Competent Person Scheme (such as APHC, CIPHE, or SNIPEF) that allows self-certification. If not registered, you must submit a Building Notice to your local authority.
What safety devices are required?
At minimum: a temperature and pressure relief valve (T&P valve), a tundish, discharge pipework to a safe external location, an expansion vessel, a pressure reducing valve, and a line strainer. CertBox checks all of these in the compliance checklist.

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