Isolation: The plumber will first isolate the section of the plumbing system to be tested. This might involve closing shut-off valves or capping off open pipe ends to create a sealed environment. For example, to test the hot water lines, the cold water supply would be shut off, and the hot water outlets would be closed.

Pressurization: Once the section is isolated, a test pump is connected to introduce pressurized air or, more commonly for water lines, water into the system. The pressure is typically raised to a specific level that is higher than the normal operating pressure of the plumbing. The exact pressure used will depend on the type of piping and local plumbing codes.

Monitoring: After pressurization, the plumber will closely observe a pressure gauge connected to the system. If the pressure holds steady over a designated time (often 15 minutes to an hour or more), it indicates that the tested section is likely leak-free.

Pressure Drop = Leak: If the pressure on the gauge begins to fall, it signifies that there is a leak somewhere within the isolated section. The rate of pressure drop can sometimes provide an indication of the size or severity of the leak.

Locating the Leak (if a drop occurs): Once a pressure drop confirms a leak, the plumber will employ various techniques to pinpoint its exact location. This might involve:

• Visual Inspection: Carefully examining all accessible pipes, joints, and connections for any signs of moisture or dripping.
• Acoustic Listening Devices: Using sensitive microphones to listen for the sound of escaping air or water, especially in concealed areas.
• Moisture Meters: Checking surrounding walls, floors, and ceilings for elevated moisture levels that could indicate a nearby leak.