Residential Plumbing Inspector Practice Test

The maximum number of fixtures allowed to be circuit vented on a horizontal branch drain is 8. Circuit venting is a plumbing method that allows for multiple fixtures to be connected to a single vent in a way that enhances the drainage while maintaining air circulation in the system. This method is commonly used to reduce the number of vents needed and to provide an efficient means of venting multiple fixtures.

The limit of 8 fixtures is based on plumbing codes, which are designed to ensure proper drainage and venting practices. Exceeding this number could lead to inadequate drainage performance or insufficient venting, increasing the risk of siphoning traps and creating negative pressure situations which can lead to sewer gas entering the living space.

In comparison, options that suggest a higher number of fixtures, such as 10 or 12, do not comply with the established standards for circuit venting and could compromise system functionality. It’s designed this way to ensure that each fixture is adequately vented and can drain properly without backflow or drainage issues arising from too many connected fixtures.