Pressurised vs vented hot water systems
A vented cylinder is fed by gravity from a cold water tank in the loft, giving modest pressure at the taps. An unvented cylinder connects directly to the mains and delivers strong, even pressure at every outlet without a loft tank at all.
Pressurised and vented hot water: the short technical version
Vented systems are simple, tolerant of low mains pressure, and cheap to maintain, but shower performance depends heavily on tank height above the cylinder. Unvented cylinders need safety devices including a pressure and temperature relief valve and an expansion vessel, and must be fitted and serviced by a suitably qualified installer under building regulations. Where mains flow is adequate, unvented systems generally give a noticeably better shower experience.
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
Practical notes on pressurised and vented hot water
- Unvented systems need no loft cold water tank
- Vented performance depends on tank height above the cylinder
- Unvented cylinders require safety valves and annual servicing
- Building regulations govern unvented cylinder installation specifically
- Mains pressure and flow rate must be adequate for unvented systems
Questions we get asked
- Can any loft be converted for unvented hot water?
- Usually, since the loft tank is removed rather than needed — mains flow is the main limiting factor.
- Do unvented cylinders need special servicing?
- Yes, an annual check of the safety devices is required, similar to a boiler service.
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Where we deal with this
Talk to us about pressurised and vented hot water
In practice: Strong, even pressure at every tap generally favours unvented, provided incoming mains flow supports it.
Use the enquiry form to describe the appliance, fault code and what changed before the problem started.
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