Illinois State Plumbing Practice Exam 2026 - Free Plumbing Practice Questions and Study Guide

The key idea is that the corporation stop is the valve on the service line where it taps into the water main. It sits at the point of connection to the main, so the utility can shut off supply to the entire property without affecting the rest of the system and without going past the meter. That’s why the correct location is at the tap to the water main. Placing a shutoff inside the building, after the meter, or in the basement would not reflect the utility-controlled point of isolation.