Vented vs Unvented Hot Water Cylinders

An Unvented Hot Water Cylinder is a pressurised system which is fed directly from the cold mains water feed and therefore can deliver hot water at mains pressure, which is great for improving the performance of your shower and bath.

Unvented Cylinders don’t require a cold water storage tank, which is ideal if you are pushed for space as well as offering more flexibility when siting the cylinder.

The water can either be heated directly via an immersion heater or indirectly via the central heating system, solar thermal technology or other renewal energy such as heat pumps and biomass.  If you are considering using multiple fuel sources, you may wish to consider a thermal store.

Unvented hot water cylinders require expansion vessels to be fitted to allow the expansion of water in the system as it heats up. Unvented cylinders also come with other safety mechanisms, such as pressure relief valves and twin thermostats. 

To ensure safety and to comply with building regulations, it is essential that an unvented hot water cylinder is installed by a G3 qualified installer and serviced annually.

POWERflow unvented hot water cylinders are some of the most popular copper unvented cylinders on the market today due to their unrivalled performance.  We also offer a range of Stainless Steel Unvented Hot Water Cylinders where budget is key.

See the full range of McDonald Water Storage unvented cylinders available for your next project.

A vented hot water cylinder is the more traditional approach where there is a cold water storage tank, often in the loft, which supplies water to the hot water cylinder on a gravity system – see schematic below.

The cold water is heated either directly from an immersion heater within the hot water cylinder or indirectly via the central heating boiler or solid fuel appliance.

The cold water tank is used to enable trapped air to escape as well as acting as an expansion tank to accommodate the expansion of the hot water during the heating process and the occasional instance of an overheat situation.

As they are relatively simple in their construction and operate at lower pressure, vented hot water cylinders tend to be cheaper than unvented.

The biggest challenge is they may deliver a lower pressure of water.

The system also takes up more space in the home with the combination of the cold water tank and the hot water cylinder.

However, on the plus side, Vented Hot Water Cylinders tend to be cheaper and require almost no maintenance.

We offer an extensive range of unvented hot water cylinders and vented hot water cylinders, many from stock. However we can also design, manufacture and supply a custom-designed vented hot water storage cylinder to suit your requirements.Contact us now on 01592 611123 to discuss your project.

McDonald Water Storage: Vented and Unvented Hot Water Cylinders across the UK and Ireland.

ECOflow Unvented Cylinder

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