Pressure transients wreak very extensive damages to water and wastewater transmission systems. Until recent years, most of the concern related to pressure transient damages was focused on the obvious extreme events of pipe burst or collapse that result in major spills or flooding. But, there are many damages, far more widespread and often more dangerous, that are less obvious and attract less attention. Pressure transients cause cracks and unseen small breaks in buried pipelines, pipe fittings and accessories. They cause joints to fracture or to come apart; they damage seals and gaskets or cause them to shift out of their sealing positions. These damages result in leakage and in contaminant intrusion and their consequent economic (water loss), environmental (infiltration of sewage to soil, water and environment), and public health (intrusion of pathogens, toxins and other contaminants to drinking water systems) repercussions. These consequences of pressure transients have come into the limelight in the past few years, and great efforts are being made to control them.

The advantages of air valves as efficient and cost effective tools for the control of pressure transients and their dangerous consequences are often overlooked or unfamiliar. Modern, well- designed, often innovative air valves can control and dampen transients, eliminating or limiting their damages. Advanced design tools, such as innovative air valve sizing, location, and specification software and vanguard transient analysis software, enable accurate and efficient air valve system protection design.
When properly sized and placed, with the help of the software, air valves can assure efficient and safe water transmission and distribution mains and force mains (wastewater pipelines under pressure), greatly decreasing piping system damage and consequent economic, health, and environmental problems.

The Problem

Pipeline systems are usually designed assuming homogeneous construction and structural integrity of the pipes and accessories, assuring leak free, efficient operation. In real life, though, this is not always the situation. Sometimes even a brand new pipeline may not be homogeneous, and some segments of pipe wall may not be uniformly thick and/or uniformly strong all around the pipe’s circumference. This is especially true for aging pipes and pipes operated under severe and/or corrosive environments. Actually, many pipelines suffer from cracks and faulty joints, seals, and gaskets. Most of these gaps go unnoticed until they result in severe pipe ruptures and pipe bursts. In the Professional and Technical Resources section of the American Water Works Association’s website, in a chapter titled “Apparent and Real Losses”, it is stated that: “ Many drinking water utilities around the world respond to leaks only after they receive a report of water erupting from a street or a complaint from a customer about a damp basement”.