In a PVC-DWV horizontal building drain

The sanitary tee is specifically not allowed in horizontal drains due to its design, which can create a blockage risk. It is intended for vertical installations where it can facilitate the flow of waste without obstruction. In horizontal runs, using this fitting can lead to issues such as clogs and backups, making it unsuitable.

The short sweep fitting is typically allowed in horizontal drainage systems. Its design allows for smoother transitions in the piping, promoting better flow without creating significant resistance or areas where waste can accumulate. Therefore, it is a suitable choice for horizontal installations.

The long sweep fitting is also permitted in horizontal drains. It provides a gradual bend that facilitates efficient flow, minimizing the risk of clogs or backups. This fitting is preferred for horizontal applications as it allows for a smoother drainage path.

The wye fitting is acceptable for use in horizontal drain lines. It allows for branching off at a 45-degree angle, which helps maintain flow direction and reduces turbulence. This fitting is designed to enhance drainage efficiency and is not associated with the issues seen with sanitary tees.