Unvented Hot Water Cylinders
An unvented cylinder is fed straight from the mains, so every hot outlet in the house runs at roughly mains pressure.
An unvented cylinder is fed straight from the mains, so every hot outlet in the house runs at roughly mains pressure. It removes the loft tanks entirely, but it is a pressurised vessel and carries its own regulatory requirements.
The safety chain
Expansion vessel, pressure reducing valve, expansion relief and a temperature and pressure relief valve, all discharging through a tundish to a safe termination. Each part has a job and none of them are optional.
Why the discharge pipe matters
Building Regulations control where hot discharge water may go. A pipe ending somewhere a person could be scalded is a fail, however tidy it looks.
Annual attention
Recharging the vessel and testing the relief valves keeps the cylinder working as intended. Skipping it is what causes weeping tundishes and pressure complaints.
What good installation looks like
- Adequate mains flow before the cylinder is chosen
- Discharge terminated where it can be seen and is safe
- Vessel charge set against measured incoming pressure
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
If your tundish drips, the water is lukewarm or the cylinder has never had a service, tell us the make and age and we will advise.
Questions we get asked
Do I need special qualifications to work on one?
Yes. Unvented hot water work is a separate competency and the installation must be notified where required.
Why is water dripping from my tundish?
Almost always a relief valve passing or a vessel that has lost its air charge. It should never be ignored or capped off.
Will an unvented cylinder fix weak showers?
Only if the incoming mains can supply the flow. Poor mains in equals poor showers out, whatever the cylinder.