A hot water system that features both a cold water storage cistern and feed and expansion cistern is referred to as what?

A hot water system that includes both a cold water storage cistern and a feed and expansion cistern is known as a double feed indirect system. This type of system functions by indirectly heating the water, using an external heat source, typically a boiler. The cold water storage cistern supplies water to the system, while the feed and expansion cistern allows for the expansion of water when it is heated, preventing any potential overflow issues and maintaining system pressure.

In this configuration, the presence of both storage cisterns enables the system to manage water supply and heating effectively, while also providing the necessary expansion capacity to accommodate the changes in water volume that occur with heating. Understanding this structure is essential for plumbers when designing or servicing hot water systems, as it plays a crucial role in ensuring both functionality and safety in the operation of the system.