If a Water Heater with a Draft Diverter is connected to a Masonry Chimney, what is the required vent size given specific parameters?

The requirement for vent size in a water heater connected to a masonry chimney largely depends on the appliance input rating and the venting system configuration. A draft diverter is designed to help manage the flow of combustion gases from the appliance into the venting system.

In this scenario, a 4-inch diameter vent is typically the correct size for standard residential water heaters with draft diverters, particularly those with higher BTU input ratings. This size is adequate to handle the volume of flue gases produced during operation and ensures proper exhaust flow, which is essential for maintaining efficiency and preventing backdrafts that could lead to dangerous situations.

Additionally, 4 inches is a common vent size for many gas appliances and is often specified in building codes and manufacturer instructions for compatibility with masonry chimneys. Ensuring the vent is appropriately sized helps to maintain the safe operation of the water heater and also supports compliance with local codes and regulations.