Unvented cylinder cost: installation and replacement prices for 2026
An unvented cylinder is what gives a system boiler or heat pump setup proper mains pressure hot water at every tap, rather than the gravity-fed pressure typical of older vented systems. It costs more than a standard vented cylinder, and the reason comes down to the safety components required by the installation standard it's fitted to.
How we read an unvented cylinder on site
In 2026, a standard 180 to 210 litre unvented cylinder typically costs £1,600 to £2,400 fitted, including the required expansion vessel, pressure and temperature relief valves, and tundish, all mandated by the installation standard for unvented systems. Larger cylinders for bigger households, or installations needing new pipework runs, additional discharge pipe routing to an external termination point, or replacement of an existing vented system's associated pipework, can push the figure to £2,600 to £3,200 or more. Installation must be carried out or overseen by someone holding the relevant unvented hot water certification, since incorrect installation of the safety components is a recognised risk this specific qualification exists to address.
Published business details
- Based at 24 Bristol Road, Radstock, BA3 3EE
- Telephone enquiries: 07516 118198
- Opening hours: Monday to Friday, 8:30am to 5:00pm
Detail that affects your quote for an unvented cylinder
- Standard 180 to 210 litre unvented cylinder typically costs £1,600 to £2,400 fitted in 2026
- Larger cylinders or new discharge pipe routing can push cost to £2,600 to £3,200 or more
- Expansion vessel, relief valves and tundish are mandatory safety components on every unvented install
- Installers must hold recognised unvented hot water certification to fit or service one
- Converting from a vented system usually needs some pipework changes alongside the cylinder itself
Questions we get asked
- What's the benefit of an unvented cylinder over a vented one?
- It delivers mains pressure hot water at every tap, including upstairs showers, without needing a loft-mounted cold water tank.
- Does an unvented cylinder need a loft tank?
- No, that's one of its main advantages, since it's fed directly from the mains rather than a gravity tank in the loft.
- Can any heating engineer install one?
- No, installation and servicing legally requires someone holding specific unvented hot water certification due to the pressurised safety components involved.
- Does an unvented cylinder need annual servicing?
- Yes, its safety components (relief valves, expansion vessel) should be checked annually alongside or separately from a boiler service.
Related help pages
- Quote structureWhat should be included in a fixed heating quote
- Cost driversStaging heating work across separate visits or phases
- ProcessHeat loss calculations: the basics behind correct sizing
- Power flushing costsCost of power flushing a heating system in 2026
- Overheat lockoutWorcester E9 overheat fault: why the boiler cut out hot
- Fault isolationBoiler faults on hot water only: isolating the DHW circuit
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Talk to us about an unvented cylinder
Where this leaves you: A properly installed unvented cylinder runs £1,600 to £3,200 in 2026, and should only be fitted or serviced by someone holding the specific certification the installation standard requires.
Published opening hours are Monday to Friday, 8:30am to 5:00pm.
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