Which fitting is acceptable for connecting horizontal drain lines?

The combination wye and 1/8 bend fitting is specifically designed for connecting horizontal drain lines due to its unique shape and angle. This fitting allows for a smooth transition and change of direction while minimizing resistance and the potential for blockages in the drainage system.

In a horizontal drain line, maintaining proper flow and preventing clogs is crucial for effective drainage. The combination wye and 1/8 bend fitting facilitates this by allowing for the side inlet at a slight angle, thus providing efficient water flow and enhancing the overall performance of the plumbing system. It is ideally suited for situations where a branch line needs to connect to a main horizontal line at a slight angle, thus ensuring that waste materials can travel freely without gathering or causing backups.

Other fittings, such as elbow fittings, are generally used for more direct turns, and coupling fittings are for joining sections of pipe without directional change. P trap fittings are specifically designed to create a water seal, which prevents sewer gases from entering the living space, but are not typically used solely for connecting horizontal drain lines. The choice of a combination wye and 1/8 bend reflects an understanding of proper plumbing practices for maintaining drainage efficiency.