ABSTRACT
A leak test is conducted at or below operating pressure to verify that a piping system is leak tight or, for certain applications such as waterworks or fire mains, that leakage is within prescribed limits. A pressure test is conducted above operating pressure, often times at 1.1 times to 1.5 times the system design pressure to verify the strength and leak tightness of a system. The leak and pressure tests defined by the construction codes are shell tests; their purpose is to verify that the fluid in the piping system does not leak out of the system. The construction code leak test is not a closure test meant to confirm that a closed valve does not leak through its seat. Seat leak tightness is addressed in Chapter 25. The leak test is a control on the quality of assembly during construction or maintenance. Most often, when leaks occur during testing they originate at mechanical joints, such as flanges or threaded connections. Leaks have also occurred, but much more rarely, in a defective weld or base metal, such as a cracked elbow, or in components, such as at a repair weld in a valve body.
