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Hot Water Cylinders

Hot water cylinders are essential components of heating systems, providing a reliable supply of hot water. There are two main types, vented and unvented hot water cylinders.

Here’s a breakdown of the differences between them.

unvented vented cylinder

Vented Hot Water Cylinders

  • Gravity-Fed: Vented cylinders rely on a gravity-fed system, where a cold water storage tank (usually located in the loft) supplies water to the cylinder.
  • Venting: These cylinders are open to the atmosphere and have a vent pipe that allows air to escape, preventing pressure build-up.
  • Simplicity: Installation is relatively straightforward and less expensive compared to unvented systems.
  • Maintenance: Typically easier and cheaper to maintain. However, the presence of a cold water tank means more potential points for issues like leaks or contamination.

Performance

  • Water Pressure: The water pressure is dependent on the height of the cold water tank. As a result, the pressure can be relatively low if the tank is not elevated sufficiently.
  • Suitability: Ideal for homes with low water pressure and where space for a loft tank is available.

Unvented Hot Water Cylinders

  • Mains-Fed: Unvented cylinders are directly connected to the mains water supply, eliminating the need for a cold water storage tank.
  • Sealed System: These cylinders are sealed and can handle higher pressures because they do not have a vent pipe.
  • Complexity: Installation is more complex and usually more expensive due to the need for safety components like pressure release valves and expansion vessels.
  • Maintenance: Requires regular maintenance to ensure safety components are functioning properly.

Performance

  • Water Pressure: Provides higher water pressure as it uses mains pressure, resulting in a more powerful flow.
  • Suitability: Ideal for homes where space is limited or where higher water pressure is desired. Suitable for delivering strong flow to multiple outlets simultaneously.

Pros and Cons Summary

Feature Vented Hot Water Cylinders Unvented Hot Water Cylinders
Water Supply Cold water storage tank (gravity-fed) Mains water supply (sealed system)
Water Pressure Dependent on tank height (usually lower pressure) Higher pressure (mains pressure)
Installation Cost Generally lower Higher due to additional safety components
Maintenance Easier and cheaper Requires regular checks on safety components
Space Requirement Requires space for a cold water storage tank No need for a cold water tank, saving space
Suitability Homes with low pressure and sufficient space for a tank Homes needing high pressure and with limited space

Unvented Cylinder Diagram

hot water cylinder

Vented Cylinder Diagram

hot water cylinder