Hydrostatic testing of water supply piping, air and water testing of DWV systems, backflow preventer field testing and certification, fixture flow verification, and the commissioning documentation and sign-off that proves an installed system actually matches its design.
A correctly sized riser and a properly vented DWV layout are still just a design until the installed piping is actually pressurized, drained, and proven to hold and perform the way the drawings promised. This module works through that verification chain in the order it actually has to happen — hydrostatic testing of water piping before it's concealed, DWV rough-in and final testing including trap seal verification, certified field testing of every backflow assembly, fixture flow rate verification against the original WSFU and Hunter's Curve design basis, and the documentation package that closes the loop with the AHJ, the water purveyor, and the owner.
It also sets up Module 17 directly: several of the next module's diagnostic scenarios — a dry trap, a failed PRV, a backflow assembly failing its annual test — trace back to a step in this module that was skipped, rushed, or never actually verified in the field.