An unvented cylinder is a hot water storage system that connects directly to the mains water supply, delivering strong, consistent pressure throughout the home without needing a cold water tank in the loft. For Croydon homeowners frustrated with weak upstairs water pressure, or living in a flat or loft-converted home without space for a traditional tank, an unvented cylinder is often the solution that finally gives a proper power shower.
What’s included
Installation covers sizing and fitting the cylinder itself, connecting it to the mains supply and existing pipework, and fitting the required safety devices - including pressure relief and temperature relief valves - that keep the pressurised system operating safely. It also covers positioning the cylinder somewhere suitable, commonly an airing cupboard, and connecting it to the boiler or immersion heater that provides the heat. Ongoing annual servicing to check the safety devices are working correctly is also part of keeping an unvented system running safely.
Why homeowners choose an unvented cylinder
The biggest draw is water pressure - because the system is fed directly from the mains rather than relying on gravity from a loft tank, showers and taps throughout the home get consistent, strong pressure regardless of which floor they’re on. Unvented cylinders also free up loft space since there’s no need for a header tank, which matters in homes that have converted their loft into a room or simply want the space back. They tend to suit homes with decent incoming mains pressure and flow, so it’s worth having that checked before committing to one.
What to expect during installation
An engineer will first check your incoming mains pressure and flow rate to confirm an unvented cylinder is a good fit for your property, then size the cylinder to match your household’s hot water demand. Installation involves connecting the cylinder to the mains and heating source, fitting the required safety devices, and testing the whole system to make sure the pressure and temperature controls are working exactly as they should before it’s signed off.
Choosing the right size cylinder
Getting the cylinder size right matters as much as the installation itself. Too small, and a busy household runs out of hot water at peak times; too large, and you’re paying to heat water you don’t need, which adds to running costs unnecessarily. An engineer will look at how many bathrooms are in use, how many people live in the property, and typical daily hot water demand before recommending a cylinder size, rather than defaulting to a standard size regardless of the household.
Why choose a Gas Safe registered engineer with the right qualification
Unvented cylinders operate under mains pressure, and UK building regulations specifically require them to be installed and serviced by someone holding a recognised unvented hot water systems qualification, in addition to being Gas Safe registered if the system connects to a gas boiler. This isn’t a job to leave to a general plumber without that specific training, since the safety devices exist to prevent a genuinely dangerous fault if the system were to overheat or over-pressurise - proper qualification matters just as much in a Croydon flat as it does in a large family home.