Unvented Cylinder Safety Checks Explained
An unvented hot water cylinder is a pressurised vessel, and its safety devices need annual checking by someone qualified specifically in unvented systems, not just general plumbing..
An unvented hot water cylinder is a pressurised vessel, and its safety devices need annual checking by someone qualified specifically in unvented systems, not just general plumbing.
Why these checks are separate from a boiler service
Unvented cylinder work is its own competency, covering the specific safety devices fitted to a pressurised hot water vessel that a standard boiler service doesn't touch.
What's checked annually
The expansion vessel's charge, the pressure and temperature relief valves, and the tundish discharge route are all inspected and tested.
What happens if something's found
A relief valve that isn't seating properly, or a vessel that's lost its charge, is flagged and can usually be corrected during the same visit.
What the annual check includes
- Expansion vessel pressure check
- Temperature and pressure relief valve testing
- Tundish and discharge pipe inspection
- General condition of the cylinder and connections
Who does the work
- Gas Safe registered engineers — registration 554328
- Worcester Bosch accredited installer
- John The Plumb Ltd, company registration 10026483
Book an unvented cylinder check
Tell us the cylinder's make and roughly how old it is and we'll get the annual safety check booked in.
Questions we get asked
Is this check a legal requirement?
It's not always a strict legal requirement for homeowners, but it's essential for safety and often required to maintain manufacturer warranty.
What's a tundish and why does it matter?
It's a visible break in the discharge pipe that lets you see if a relief valve is passing water, an early warning sign not to ignore.
Can any plumber carry out this check?
It needs someone specifically qualified in unvented hot water systems, which is a distinct competency from general plumbing or gas work.