Water Hammer Causes Water Main Breaks

Abstract

Abstract Most underground water main breaks can be stopped, since the technology is now available to evaluate water system piping failures and determine corrective actions. The problem is defined in terms of several variables: (1) Water hammer is the initiator of nearly all underground water main breaks. (2) In nonacidic soils, fatigue directly causes piping cracks. (3) In acidic soils, water hammer cracks the pipes, and crevice corrosion is accelerated at those crack sites. Additionally, those cracks serve as moisture sources to induce piping surface corrosion due to galvanic corrosion between the soil and the metallic pipe wall. Even so, some failures are solely due to corrosion. (4) Dynamic pipe stresses are significantly larger than stresses caused by static loading, i.e., hoop stresses and strains may be as much as four times the calculated static stress due to water hammer. (5) If dynamic stresses are not considered, calculations incorrectly conclude that water mains will not be damaged. (6) That is, water hammer calculations determine pressure surge magnitudes that are multiples of the operating pressures, where dynamic effects cause fatigue cracks due to the applied pressures and the number of cycles for those pressures to break water mains.