Hot Water · Glossary
Unvented Cylinder
A pressurised hot water cylinder fed directly from the mains, delivering balanced mains-pressure hot water to all outlets without a loft tank.
An unvented cylinder is a sealed pressurised hot water store fed directly from the cold water mains. Outputs are at mains pressure (typically 2-4 bar in Cornwall), giving powerful balanced hot and cold flow to bathrooms — no separate cold water tank required and no gravity limitations.
Installation is regulated under Building Regulations Part G3 and must be carried out by a G3-qualified engineer. Common brands include Megaflo Eco, Telford Tempest, Joule Cyclone and Mixergy iHP. Sizes typically range from 150L (1-bed flat) to 300L (5-bed family home).
Cornwall water is moderately hard to hard depending on location (Camborne and Redruth around 250 mg/L CaCO3) so we always include a phosphate scale inhibitor on the cold feed and recommend annual descaling on the immersion element. See our cylinder installation page or call 01209 596 002.