Unvented Cylinders

Unvented Cylinder FAQs

What’s the difference between a direct unvented cylinder and an indirect unvented cylinder?

Unvented cylinders are available as either direct or indirect. Both are unvented cylinders and therefore connect to the mains water supply to offer powerful flow rates. The difference between these two types of unvented cylinders is therefore in reference to where and how the water in heated in the system.

With direct unvented cylinders, the water is heated ‘directly’ by the cylinder itself. An immersion heater within the cylinder is therefore used to provide hot water around your home. Some direct unvented cylinders contain more than one immersion heater to provide a faster and more powerful supply of hot water around your home.

Indirect unvented cylinders however rely on external appliances to provide ‘indirect’ heat to the system. This is typically a boiler, but may also include solar panels. Hot water generated by an indirect cylinder is stored and can be used as a backup should the main heat source fail.

Is my mains water supply suitable for an unvented cylinder?

Unvented cylinders require the mains water pressure to be ideally a minimum of 1.5 bar dynamic pressure. Many unvented cylinders are able to work with pressures as low as 1 bar dynamic pressure however you should consult with your heating engineer or the manufacturer for guidance on this, as weak pressure will compromise the performance of your central heating system.

Do unvented cylinders need to be serviced?

All manufacturers advise servicing your unvented cylinder annually by a Gas Safe qualified heating engineer. Failing to do so may invalidate your warranty.

Can unvented cylinders be installed in basements?

Most unvented cylinders can be installed anywhere in your home however it’s worth considering that a discharge pipe is usually required.