Unvented Cylinder Servicing

Unvented cylinders require servicing annually and its more important than most people realise.

There are various safety valves/devices fitted on unvented cylinders, these let water out when the pressure reaches a certain level should the expansion vessel fail, which they do, a lot.


So an annual inspection is required to check the expansion vessel and these safety devices, and manufacturers require an annual service to maintain the warranty should the cylinder fail and leak.


Here is a list of checks that should be carried out during a service (as a minimum);

- Checking water flow rate & temperature

- Cleaning of line strainer where possible

- Testing of pressure relief valve.

- Testing of temperature/pressure relief valve.

- Testing of safety cut off devices.

- Testing of immersion condition/resistance.

- Check drain off works.

- Checking expansion vessel pre charge/reinstate air gap.

- Visual inspection of the unit.


Any engineer carrying out work on any unvented cylinder must have their unvented certification (referred to as G3), here at HiPro Heating we only have G3 qualified engineers and cover the Yorkshire area.


Cylinders that haven't been maintained or inspected can and do split. If this happens it just like opening a tap onto the floor and can wreck properties, especially apartments where the water can travel down 5 or more floors.


I have known home insurance policies that have been void when a cylinder has split, as they can class the lack of maintenance as neglect. They then won't cover the cost of replacement and repair to the property.

As an authorised independent Kingspan service engineer, we can provide a better than manufacturers service and service your gas boiler at the same time. Single appliance services start from £60 plus VAT and dual appliances from £100 plus VAT depending on location.