Combination drain and vent pipe shall have a maximum slope of?

The maximum slope for a combination drain and vent pipe is designed to ensure proper drainage and venting of the plumbing system while preventing the accumulation of waste or air pockets that could lead to clogs or ventilation issues. A slope of one-half unit vertical to 12 units horizontal allows for efficient waste flow while maintaining adequate venting. This configuration strikes a balance between facilitating the movement of liquids and ensuring that venting remains effective, preventing negative pressure and enabling air to circulate properly in the system.

Other options suggest steeper slopes or different ratios, which might compromise the effectiveness of the drainage or venting system by creating conditions where waste could settle, leading to potential blockages. Therefore, the one-half unit vertical to 12 units horizontal slope is the optimal standard recommended for these types of pipes, ensuring both functionality and compliance with plumbing codes.