Heat-Only Boiler

Also called a "regular" or "conventional" boiler — a heat-only unit feeding a hot water cylinder via a vented header tank in the loft.

A heat-only boiler (also called regular, traditional, or conventional) is the simplest design. It fires water that flows by gravity or pump to radiators and a hot water cylinder. A small feed-and-expansion tank in the loft provides make-up water and accommodates expansion. A separate cold water storage tank in the loft feeds the hot water cylinder by gravity.

Heat-only setups are still common in older Cornish properties because they were the standard until the 2000s. They are reliable but inefficient on space, prone to loft tank issues (frozen pipes, contamination), and deliver only gravity-fed hot water pressure to the bathrooms.

For most upgrades, CCS recommends moving from heat-only to either a combi (small property) or system boiler with unvented cylinder (larger property). See our boiler installation page.