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Hot Water Cylinders

A Cylinder is a water tank used for storing hot water for space heating or domestic use. Most hot water cylinders are heated via an external heat source such as a gas boiler or solar thermal.

We stock all types of hot water cylinders, from unvented and vented, to copper cylinders and immersion heaters, so you’re sure to find a model that’ll suit your installation requirements. All our hot water cylinders come with free delivery as standard and varying levels of guarantees, including a lifetime guarantee on selected models.

Please note all cylinder purchases must be made online and cannot be made via the customer service phone line. Any incorrectly purchased hot water cylinder that you wish to return will involve a restocking fee and expensive carriage charges.

For more information, visit our cylinder guide or get in touch with your Gas Safe registered heating engineer for technical advice.

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Hot Water Cylinder Help & Advice

If you’re not a heating engineer, hot water cylinders may seem confusing. In basic terms however, the hot water cylinder you’ll need for your property will depend on 2 things; how you intend to heat the water in your central heating system and how you want the hot water to be distributed around your home.


What Is A Direct Cylinder?

The water in a direct cylinder is heated ‘directly’ by the cylinder itself. Other appliances, such as boilers or solar panels are not used to generate the hot water within the cylinder. Instead an immersion heater within the cylinder is used to heat the water.

Some cylinders have more than one immersion heater contained to provide faster access to hot water.

Direct cylinders are available as either ‘vented’ or ‘unvented’, both indicating a different method through which hot water is distributed around your home.


What Is An Indirect Cylinder?

Indirect cylinders rely on external appliances to apply heat to the cylinder. This in turn heats the stored water within the cylinder and can be used as a backup if the main heat source fails. Water within the cylinder is indirectly heated by other appliances including boilers and solar panels.

A heat exchanger within the cylinder transfers heat from the external appliance to the water in the cylinder. Some indirect cylinders may contain immersion heaters that enable the cylinder to add additional heat to the stored hot water. For this reason an indirect cylinder tends to be able to generate hot water faster than a direct cylinder. Direct cylinders can be either vented or unvented, depending on how the hot water is distributed around the property.

What Is An Unvented Cylinder?

If you need a cylinder that uses the mains water pressure to distribute the hot water around your property for use at your hot water outlets (i.e. taps, showers) then you will need to invest in an unvented hot water cylinder.

Unvented cylinders are commonly used as part of a system boiler installation as they’re able to take advantage of the high pressure water supply associated with system installs. If you have limited space in your loft then you will be pleased to hear that unvented cylinders take up less space than vented cylinders as no feeder tank is required.


What Is A Vented Cylinder?

Vented hot water cylinders rely on a feeder tank to provide it with mains fed cold water. This water is then heated and distributed to the hot water outlets as part of a gravity led system. As such, your amount of loft space will be slightly reduced as an additional feeder tank will be required.

Vented cylinders tend to be used alongside regular boiler installations, whereas unvented cylinders are commonly used with system boiler installations.

For more information or advice, visit our hot water cylinder guide or seek the advice of a Gas Safe registered heating engineer.