Unvented cylinder
A hot water cylinder fed straight from the mains and run under pressure, with no open vent or tank in the loft.
Its safeguards include a temperature control, an independent overheat cut-out, expansion space and a relief valve that discharges through a tundish. Our lessons teach you to recognise them and hand the work over to a competent installer, by the route the nation sets.
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Sources
Sources checked 31 October 2026. Guidance, grants and official pages can change.
- Government guidance: Building regulations approvalInstalling or replacing a heating system needs building regulations approval in England and Wales unless a competent person scheme member does it; Scotland and Northern Ireland have their own rules.