Open Vented Systems
This is usually on older systems and cast iron boilers. This means that there is an Expansion Tank fitted high up, which feeds the water down the Cold Feed into the central heating system. This is usually fitted in the loft next to the storage tank. We don’t install these systems any longer.
Instead of using an expansion tank and an expansion pipe, sealed systems use an Expansion Vessel, a Safety Relief Off Valve and a Filling Loop. Most modern systems use this method because it is easier to install and has less tendency to develop problems in the system at a later date.