__________________________ is the maximum allowable length of a 2 inch horizontal waste arm from the combination wye and 1/8 bend fitting to the fixture connection before a revent is required?

The maximum allowable length of a 2-inch horizontal waste arm from the combination wye and 1/8 bend fitting to the fixture connection is 5 feet before a revent is required. This guideline is based on plumbing codes that aim to ensure proper drainage and venting of plumbing systems.

In plumbing, waste arms are crucial for managing the flow of wastewater from fixtures. If the horizontal run of the waste arm exceeds the specified length without venting, it can allow negative air pressure to develop, which may impede drainage and lead to potential siphoning issues. Since a 2-inch waste arm has a specific capacity for carrying waste, limiting its length helps maintain consistent flow and prevents clogging.

By adhering to the 5-foot maximum, plumbers ensure that sufficient venting is provided to allow air to enter the system, which helps maintain the flow and proper operation of the fixtures. Therefore, understanding these limitations is essential for maintaining compliance with plumbing codes and ensuring the efficiency of waste drainage systems.