On completion the service is flushed until clear, then pressure tested before burial or concealment (the 2003 text required no leakage at 1500 kPa for at least 30 minutes, joints exposed on rubber ring systems); storage tanks other than rainwater tanks are filled to overflow and the air gap verified (2003 Section 16).
The graph holds this control, the 0 it maps to, and the evidence behind each claim, over MCP and REST.