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Witten by Bernard Morgan (Engineer) & Adam Apperley (Marketing).
Published: February 15, 2024. Updated: February 15, 2024

Vented vs Unvented Cylinder – Which is better?

Vented vs Unvented Cylinders - Which is best | Boilerhut

If you have a system or regular boiler, domestic hot water cylinders are essential for everyday activities. There are two main types of hot water cylinders: vented and unvented. Each is suited to specific types of properties and central heating systems.

Due to their efficiency, unvented cylinders have become popular, especially in new-build homes.

Unvented Cylinders

Introduced in the UK in 1986, unvented cylinders store hot water from the mains. This eliminates the need for a cold water tank in the loft.

This direct connection increases water pressure and a more consistent flow rate. This makes unvented systems more efficient and less space-consuming than their vented counterparts.

Unvented cylinders are sealed, preventing water contamination and providing quieter operation. They heat water through the home’s boiler or an electrical element. They can be placed anywhere within the property, offering installation flexibility.

Vitocell 300-V 500 Litre Unvented Cylinder

Vented Cylinders

Vented cylinders, or gravity-fed hot water systems, are traditional in the UK. These systems rely on a cold water tank in the loft to supply water, utilising gravity to generate water pressure.

They are cheaper than unvented systems. But, vented cylinders provide lower water pressure. This is especially noticeable in outlets further from the cold water tank. Pumps can be installed to improve pressure. However, the system’s design provides less pressure than unvented systems.

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Converting Vented to Unvented Cylinders

It’s not always possible to convert a vented cylinder directly into an unvented system. This is due to the differences in pressure and design. But upgrading your entire system to accommodate an unvented cylinder is possible. It may also be more cost-effective as part of a broader heating system upgrade.

Vented vs Unvented Cylinders – Choosing the Right Cylinder

The choice between vented and unvented cylinders depends on several factors. These include your current heating setup, mains pressure, property size, and budget considerations.

Unvented systems are ideal for newer properties or renovations. Especially where higher water pressure and efficiency are desired. In contrast, vented systems may be more suitable for older homes with existing low-pressure pipework. They can be the better option where mains water pressure is low.

Installation Considerations

Regardless of the type you choose, professional installation is crucial. For unvented cylinders, assessing your home’s unique needs ensures you select the right size and type for optimal performance.

Vented systems require sufficient space for a cold water tank and appropriate pipework, which might be more disruptive during installation.


Understanding the differences between vented and unvented hot water cylinders allows homeowners to make informed decisions suited to their specific needs, ensuring efficient and reliable hot water supply throughout their homes.

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