Illinois Plumbing Code Practice 2025 – 400 Free Practice Questions to Pass the Exam

The correct answer is 2 pipe diameters. According to the Illinois Plumbing Code, a trap vent is required to maintain proper drainage and prevent sewer gases from entering the home. It is critical that the vent is placed a specific distance from the trap weir to ensure effective venting and to prevent any potential siphoning of the trap fluid, which could compromise its function.

Installing a trap vent too close to the trap weir could lead to issues with drainage, as it may allow air pressure to influence the seal provided by the trap. The statute defines this required distance as a minimum of 2 pipe diameters, ensuring that the venting system functions optimally and maintains a proper air balance in the drainage system.

Other distances, such as 1, 3, or 4 pipe diameters, do not align with the regulations set forth in the plumbing code, which specifies 2 as the necessary distance to avoid complications associated with drainage and trap performance.