Unvented Cylinders

All unvented hot water cylinders have to be installed by a registered company for safety and proper installation. All unvented water storage units need to be checked and serviced every year for safe operation.

The unvented cylinders that we install are constructed from stainless steel with an internal expansion known as bubble top cylinders (no need for external expansion vessels) which makes them smaller and easy to install in most areas of the home.

These unvented cylinders do not require a sacrificial anode to stop internal corrosion so peace of mind for years of use. The unvented cylinders come with a 25 year guarantee on the cylinder and 1 year guarantee on all valves and thermostats.

All unvented cylinders will have to be notified to building control before installation and registered when installed. There are a number of advantages and disadvantages of an unvented hot water cylinder are:


  • Balanced pressures at both hot and cold taps
  • High performance showering throughout the house
  • Faster filling baths
  • Certainly no cold water tanks in the loft space to be contaminated or to freeze in winter
  • Quick installation and quiet in operation
  • Fast heat recovery (typically 23 mins for 170L)
  • It can also be fitted anywhere in the thermal envelope of the property
  • Minimal heat loss, performance exceeds CHeSS best practice and Part L of building regulations
  • Faster flow rates than any combination boiler unit and still keeping the immersion heater backup
  • Mains pressure possible water at all outlets, up to 55 litres per minute


  • No storage back up if the mains water fails
  • Poor mains water pressure will cause poor performance
  • Need for a discharge pipe (overflow)
  • Requires servicing yearly

Unvented hot water storage cylinders can be heated directly via an immersion heater or indirectly by most heating systems providing it is not a solid fuel burning appliance (e.g. it has to be a controllable heat source). These cylinders are ideal where high performance is required or in multi story properties where it would be difficult to gain the necessary head of water via a cold water storage tank to feed taps on the upper floors.

To book an appointment, contact our office on 0208 422 9780, or email us by clicking here. A member of staff will contact you as soon as possible, to arrange an appointment for the earliest date and time that best suits you.

You’ll be able to find out more about the services we offer by heading over to; http://amserviceslondonltd.co.uk/services/.