What is the maximum number of fixtures that can be connected to a horizontal branch drain and be circuit vented?

• A. Six
• B. Seven
• C. Eight
• D. Nine

Answer: (C)

The maximum number of fixtures that can be connected to a horizontal branch drain and be circuit vented is eight. This standard is established in plumbing codes to ensure that the drainage system functions effectively while minimizing the risks of blockages and maintaining proper ventilation.

Circuit venting allows for the installation of multiple fixtures in a way that the venting system is shared, which can save space and materials. However, limiting the number of fixtures to eight helps to balance the flow capacity of the drainage system while ensuring that there is sufficient venting to prevent siphoning and maintain trap seals. This is important to avoid creating negative pressure that could lead to sewer gases entering the building or cause drainage issues.

The other numbers are below and above this limit, therefore inadequate or excessive for maintaining both adequate drainage performance and effective venting in accordance with plumbing codes.