Water heating & storage with cylinder installations can involve two different systems, Vented and Unvented.
Unvented hot water cylinder installations are very space-efficient as they utilise a pressurised system which is fed directly by the cold mains water feed, allowing the heated water to be delivered at a higher pressure. The cylinder heats the water using a heating element or coil within a boiler or immersion heater, where the hot water is stored. The hot water within this system can also be heated through secondary routes via the central heating system or renewable energy systems e.g. solar or thermal, allowing the system to be more cost-effective.
Vented cylinder systems are more traditional and use a cold water storage tank, often located in the loft, which supplies water to the installation. Here the water is once again heated directly using an immersion heater within the cylinder or through the central heating boiler. While the water pressure is lessened in this system, the overall cost and maintenance requirements are also reduced.