You probably need an unvented hot water cylinder if your home has two or more bathrooms used at the same time, your showers are weak on a tank-fed system, or a combi boiler can’t keep up with demand. An unvented cylinder stores hot water at mains pressure, giving strong flow to several taps and showers together.
It only works well with good incoming mains pressure and flow. Measuring those is the first step. Our hot water solutions page explains the options we install.
Signs it could help
- More than one bathroom, with showers used at the same time
- Weak showers from a loft-tank system
- Mixer showers that are hard to balance
- A combi boiler that struggles when two taps run
- Loft tanks you’d like removed, perhaps for a loft conversion
How it compares
| Unvented cylinder | Combi boiler | Vented (tank-fed) cylinder | |
| Pressure | Mains | Mains | Low (gravity) |
| Several outlets together | Strong | Limited | Weak pressure |
| Stored hot water | Yes | No | Yes |
| Loft tanks | No | No | Yes |
| Suits | Larger homes | Smaller homes | Low mains pressure |
What’s needed to fit one
- A check of mains pressure and flow
- A cylinder sized for your household
- Safety devices: temperature and pressure relief valves, expansion vessel, pressure-reducing valve
- A discharge pipe run to a safe outlet
- A system or regular boiler (or heat pump) to heat it
- A qualified installer, with the work notified under Building Regulations
Yearly checks
Unvented cylinders need their safety devices checked annually. It’s usually done with the boiler service and is often required for the warranty.
Unvented cylinders in Oxfordshire homes
Many homes around Abingdon, Didcot, Wallingford and Oxford have been extended over the years, adding en-suites and extra bathrooms to a system designed for one. That’s where an unvented cylinder often makes the biggest difference. Older period homes may still have loft tanks and gravity-fed systems that could benefit too, provided mains pressure is good. Our post on the best boilers for period homes looks at heating choices for older properties.
If the rest of your heating needs attention too, see our heating page.
Frequently asked questions
What if my mains pressure is low?
An unvented cylinder won’t perform well with poor mains pressure or flow. Other options, like a pumped vented system, may suit better.
Do unvented cylinders have a backup?
Most include an immersion heater, so you can still heat water if the boiler is out of action.
How long does installation take?
Often a day or two, depending on pipework changes and whether loft tanks are being removed.
Get better hot water
Fancy stronger showers or more hot water? Ring us on 01865 817 611 or send us a message and we’ll talk you through what would work in your home.
