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Choosing Your Water Heater: Is a Vented or Unvented Cylinder Better?

5 Jun 2020
Whether you’re building a new home or you’re improving your current home’s hot water system, you have many decisions to make. One of the most important is whether to use a vented or unvented cylinder. Is one better than the other? Actually, there are quite a few differences here. It’s important to make an informed decision, so we’ll walk you through the factors to consider.

What’s the Difference between a Vented and Unvented Cylinder?

Actually, the primary difference between these two types of water cylinders is right there in the name. A vented cylinder vents to the outside. It’s not pressurised. An unvented cylinder is not vented, and it is pressurised. However, while that difference might be obvious, it doesn’t really explain how each system works in your home.

With a vented cylinder:

  • The cylinder must be installed high up in the home because the hot water is gravity fed.
  • There is a secondary cold-water tank that may freeze in winter if not properly protected.
  • You do not have mains pressure hot water, which can make showering and washing up less enjoyable.
  • There is no danger of overpressure situations.

With an unvented cylinder:

  • The cylinder can be installed almost anywhere, and it requires less room.
  • There is no secondary cold-water tank needed.
  • The cylinder connects directly to the mains for improved water pressure throughout your home.
  • There is a risk of overheating and overpressure situations, but multiple safety devices are built in to prevent these issues.

Other Considerations

As you can see from the information above, unvented cylinders are generally better suited to modern life. However, that may still not be the right choice for your home. For instance, if you have a vented cylinder currently, connected to a regular heating system, then an unvented cylinder might over pressurise your heating system, causing problems.

Another issue here is the mains pressure. If your mains pressure is low, an unvented cylinder is not going to improve things very much. Instead, you may need to have a pump installed to improve water pressure.

Yet another consideration is the number of people in your home and the number of bathrooms you have. If two or more bathrooms will be used at the same time, this can create a drop in pressure for both with an unvented cylinder. With an older, vented-style cylinder, the cold-water tank ensures ample volume to prevent a pressure drop, although the system’s pressure will be lower than with an unvented cylinder in the first place.

Moving Forward

While unvented cylinders are usually the better option, that is not always the case. It’s important that you make an informed decision based on the specifics of your home, your family, and your use needs. The best way to do that is through a professional assessment. Contact EasyFlow today on 0161 941 5571 to schedule an in-home consultation with one of our G3-certified plumbers to determine whether you would benefit from an unvented cylinder.


Unsure whether to install a vented cylinder or an unvented cylinder? It can be quite challenging. While most UK homes are best off with a modern unvented cylinder, that is not the case for every home. A number of factors should be considered.

First, you should begin with an understanding of how vented and unvented cylinders stack up to one another. In general, unvented cylinders do not create the same water pressure as vented cylinders, require more space for installation, and must be installed near the top of the home. Unvented cylinders offer mains pressure water, can be installed almost anywhere, and require less space, but must be installed by specially licensed plumbers (G3-compliant).

You also need to consider other factors, including the number of people in the home, the number of bathrooms, whether you’ll connect the cylinder to your central or underfloor heating system, and more. Call EasyFlow today to schedule a professional consultation. One of our G3-licensed plumbers will be happy to discuss your needs and help ensure that you get the best water heater for your home and your family’s needs.

EasyFlow can send an engineer to you if you’re located in Greater Manchester, Warrington, Liverpool and Chester.


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