What is the main difference between vented and unvented hot water systems?

The primary distinction between vented and unvented hot water systems is that vented systems are open to the atmosphere, which allows air to enter and exit freely within the system. This is achieved through a vent pipe that connects to the storage tank, ensuring that water can expand and contract without generating dangerous pressure. As a result, vented systems typically operate at atmospheric pressure.

In contrast, unvented systems are sealed units that operate under pressure. These systems do not require a vent pipe because they maintain a safe, pressurized environment that allows for higher service temperatures and better flow rates. The sealed design prevents air from escaping, enabling the system to deliver hot water more efficiently and maintain consistent pressure.

Understanding this key difference is crucial for plumbing professionals, as it impacts installation requirements, safety considerations, and the overall functionality of the hot water systems in use.