How unvented cylinders work
Mains pressure vs gravity
A traditional vented cylinder is fed by a tank in the loft, and pressure depends on the height of that tank. An unvented cylinder is fed directly from the mains, so pressure is much more consistent.
Safety devices
Unvented cylinders include safety devices such as temperature and pressure relief valves, an expansion vessel and a discharge pipe. These must be installed and routed correctly, which is why G3 qualification is required.
Checking your supply
An unvented cylinder can only perform as well as your incoming mains supply. We measure pressure and flow before recommending one.
Working with your boiler
Unvented cylinders are heated by a system or regular boiler. If you're considering a new boiler at the same time, we'll recommend a matching setup.
Annual checks
Unvented cylinders should be checked regularly to make sure safety devices are working. We can do this alongside your boiler service.
Choosing the right cylinder size
Cylinder size depends on how many people live in the home, how many bathrooms there are and how much hot water you use at the busiest times, such as the morning rush. Too small and you run out; too large and you pay to heat water you don't use. We'll recommend a size based on how your household actually lives, not a one-size-fits-all figure.
Space matters too. Unvented cylinders often fit in the same airing cupboard as an old vented cylinder, but the safety pipework needs a suitable route, which we plan during the survey.
Unvented cylinder or combi boiler?
Both give you mains-pressure hot water, but in different ways. A combi heats water on demand and needs no cylinder at all, which suits many smaller homes. An unvented cylinder stores hot water ready to use, which suits homes with more than one bathroom where several taps and showers may be used at once. We'll help you decide which fits your home and give you a clear quote for either option.
Replacing an old hot water tank
If your existing cylinder is leaking, slow to heat up, or covered in corrosion, replacement is usually the sensible option. We remove the old cylinder, fit the new one neatly and test everything before we go. Customers have described our cylinder work as very neat and tidy, and we check back to make sure everything is working as it should.
Working with heat pumps
If you're considering an air source heat pump in the future, it will usually need a hot water cylinder. Planning the cylinder with that in mind can make a future upgrade simpler.
Why the discharge pipe matters
Every unvented cylinder has a discharge pipe (often called a tundish arrangement) that safely carries away water if a safety valve ever opens. It has to be the right size, run to a safe termination point and be visible where it's required. It's one of the details that separates a correct installation from a dangerous one, and it's exactly what G3 training covers.
When we survey your home, we plan the discharge route along with the cylinder position, so there are no surprises on installation day.
Where we work
We carry out unvented hot water cylinders for homeowners and landlords across Fareham, Gosport, Stubbington, Portsmouth, Southampton, Titchfield, Portchester, Lee-on-the-Solent, Locks Heath, Park Gate, Warsash and Whiteley.
