What’s the difference between a vented and an unvented water cylinder?

Published on February 3, 2025

Water Cylinder blog image

A water cylinder is at the heart of the operation of every boiler, delivering essential heating and a steady hot water supply for your home.

But unless you have replaced a central heating system – in most cases likely to be a once in a generation job – you probably haven’t considered replacing or upgrading your water cylinder, that large vessel that does such an important job.

So as one of Wigan, Leigh, Lancaster and Morecambe’s most highly-rated and respected installers of unvented and vented water cylinders, boilers and central heating systems, and a Which? Trusted Trader, in this article RJ Martindale’s expert boiler and water cylinder installation engineers give you an idea of what your water cylinder does, the main types of water cylinder on the market, and the differences between them.

Then, when you need to start looking for the best new vented or unvented water cylinder or central heating system for your property, needs and budget, you won’t be caught cold.

What does my central heating’s water cylinder do?

The water cylinder either takes water directly from your property’s mains water supply, or stores it separately – usually in a tank in your loft or other space on the upper floor – then controls how it is delivered to your taps and the other appliances that need it.
Whether you choose vented or unvented cylinders, if they are properly fitted and well maintained, both types will work well under normal water pressure conditions.

Water cylinders come in two types:

– Unvented: These are integrated into the workings of the hot water supply system, so they don’t have a separate storage tank. The water in an unvented water cylinder will be heated by either an immersion heater – which is a bit like a large kettle – or by the heat created by your gas boiler, similar to how a ring on a gas hob works.

– Vented: A vented water cylinder stores water separately from the immersion heater or boiler, but get their supply from a separate cold water tank. Usually found in your loft, this feeds water into the hot water cylinder by gravity.
Your home and water heating experts at RJ Martindale will be able to advise you on the right choice between vented and unvented cylinders, based on your type of property and water supply set-up, and your family’s specific needs.

Why choose an unvented water cylinder?

Whereas the water supply from a vented water cylinder can sometimes suffer from low pressure, especially in older houses, the water supplied via an unvented cylinder doesn’t have as far to travel, which means your supply is more likely to stay at a consistent pressure, no matter how far the tap (or shower) is from the water tank. An unvented water cylinder is therefore a good choice if you do otherwise suffer from low, or inconsistent, water pressure levels.

Other instances where you may benefit from installing an unvented water cylinder include:

– If you don’t have a suitable space close to your boiler, as unvented water cylinders can be fitted almost anywhere
– If you get some or all of your power via solar panels, as the water in an unvented water cylinder can stay hot for longer, including times when not much power is being generated
– If you use a lot of hot water
– If you want a system that you can practically ‘fit and forget’ – once in place, an unvented water cylinder needs very little maintenance

Why choose a vented water cylinder?

A vented water cylinder works best alongside an older heating system. As they don’t take their water supply from the mains, vented water cylinders are ideal for a property that is either not connected to this supply, or which suffers from intermittent supply difficulties. A vented water cylinder will also work well if you get some of your power from solar panels.

A vented water cylinder is a great option if:

– The age or condition of your heating system means you suffer from low water pressure
– You want the cheapest long-term option – no mains connection means there is less pipework to look after and worry about keeping working at its most efficient
– You need the extra assurance of having a back-up supply, as this will be provided directly from the immersion heater, should the water in the vented water cylinder run out

Install unvented and vented water cylinders with RJ Martindale’s Gas Safe Registered team in Wigan, Leigh, Lancaster & Morecambe

Installation of unvented and vented water cylinders should be carried out by an accredited Gas Safe Registered engineer, ensuring your new water cylinder, boiler and central heating system operates to its best. RJ Martindale’s installation engineers throughout the North West are Gas Safe Registered, fully trained and accredited, giving you the reassurance you need that your home’s in safe hands.

Installing unvented and vented water cylinders, boilers and central heating systems in Wigan, Leigh, Lancaster and Morecambe, we’re one of the North West’s most trusted water cylinder, boiler and central heating installation organisations, protecting homes, families and investments with fully-qualified, reliable and experienced gas boiler services.

With hundreds of five-star Google reviews for our work, we take the heat out of finding the right type of water cylinder, and the answers to your complete water and home heating installation and maintenance needs, across the Wigan, Leigh, Lancaster and Morecambe areas.

Time to install your new water cylinder? Book a FREE survey with RJ Martindale’s local team of Gas Safe Registered engineers. We’ll recommend water cylinder models to suit your budget and your household’s needs from a range of leading manufacturers, before installing your new water cylinder promptly.

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