Water Hammer Induced by a Line Break

A sudden break of a pressurized and dead-ended water main induces water hammer and possibly column separation at the dead end. Because a line break is an energy venting and depressurizing event, one may not anticipate overpressures as a result of the break. The purpose of this paper is to show that a line break can generate excessive overpressures severe enough to cause damage. Through analysis and laboratory tests, we demonstrate that (1) if column separation does not occur at the dead end of the main line, the transient pressure in the main does not exceed the initial pressure in the main prior to the break; (2) if column separation occurs, the transient pressure in the main can exceed the initial pressure; and (3) damaging overpressure in the connected service lines may occur whether column separation occurs in the main or not.