Both systems store hot water, but they deliver it differently. The right choice depends on the property, available water pressure and how much hot water is used at the same time.
What is a vented cylinder?
A vented cylinder is supplied by a cold-water storage tank, usually in the loft. It is a familiar, straightforward arrangement that can suit properties with an existing gravity-fed system.
What is an unvented cylinder?
An unvented cylinder takes water directly from the mains. When the incoming supply is suitable, it can provide stronger pressure and serve more than one outlet without needing a cold-water tank.
VentedFed from a storage tankUsually lower pressureWorks with many traditional systems
UnventedFed directly from the mainsPerformance depends on mains flow and pressureRequires specific safety controls
What should be checked first?
- Incoming mains flow and pressure
- Available space and existing pipework
- How many outlets may run together
- The property's heating and hot-water demand
Safety matters.
Unvented cylinders use dedicated safety devices and discharge pipework. Scottish guidance calls for installation by a person with the appropriate training and practical experience.