Which type of plumbing system uses a central water heater?

A plumbing system with a continuous circulation loop employs a central water heater to maintain a steady supply of hot water throughout the system. In this configuration, the water is heated in a central location and then circulated through the pipes to various fixtures within a building. This setup allows for faster access to hot water by reducing the wait time for hot water at the tap since the system is designed to keep water at a consistent temperature and readily available.

In contrast, a decentralized water heating system involves multiple water heaters placed throughout the building, providing hot water at the specific location where it's needed without relying on a single central source. A tankless water heating system heats water on demand and does not store hot water in a central unit, thus eliminating the concept of a central water heater. Finally, a drainage-only plumbing system lacks any water heating component altogether, focusing solely on wastewater removal and management.