Common Defects in Plumbing & Piping Failures Expert Article

The engineers at Robson Forensic frequently investigate matters where property has been damaged by water, gas, or another substance leaking from a failed plumbing system. These leaks often originate from a pipe, a pipe fitting, a tank, or an appliance. Identifying the cause of the incident requires the consideration of the type of system (water, gas, sewerage, etc.), the type of piping, and any external conditions that may have contributed. 

In this article, Mechanical Engineer and Building Systems expert Stanley Jaworski explores common failure modes in commercial and residential plumbing systems.

Plumbing failures expert article

Common Defects in Plumbing & Piping Failures - Expert Article

In a typical plumbing failure case, our experts are tasked with determining whether a failure was a result of a product defect, a defective installation, or neglected property maintenance. These cases can be complicated and may involve a combination of factors. For example, the effects of a minor defect can be exacerbated by a flaw in the installation, or vice versa. After investigating hundreds of these incidents, we have compiled a short list of the conditions that commonly cause or contribute to the failure of plumbing and piping systems.


Plumbing fittings and valves are commonly made from brass, which is an alloy (mixture) of the metals copper and zinc. While other metals may be added to modify the properties of the brass, the primary constituents remain the same. Dezincification, in simple terms, is a process whereby the zinc migrates or is leached out of the alloy. The remaining material, after the zinc has leached out is an increasingly brittle and porous copper structure that is prone to failure.

Photo: dezincification plumbing

Brass is an accepted material for use in plumbing and in potable water systems, but it is important that the material used meets the required specifications. Where a forensic investigation finds evidence of dezincification, an analysis of design specifications or a materials analysis of the failed component(s) may be required. Generally, brass alloys with more than 15% zinc are more susceptible to dezincification.

Dissimilar Metals

Galvanic corrosion (sometimes referred to as bimetallic corrosion) is an electrochemical process in which one type of metal corrodes preferentially when it is in electrical contact with another type, in the presence of an electrolyte such as water. Galvanic corrosion can occur when dissimilar metals are joined together without the use of appropriate measures to prevent electrical conduction between materials. Appropriate measures typically include separating the dissimilar metals with a non-conductive component such as a rubber washer or plastic fitting. The solutions to the electrochemical process of corrosion are universally understood by plumbers and pipe fitters and are often addressed in plumbing codes.

Despite the causes of galvanic corrosion being well known within the industry, and some connection types being prohibited in the plumbing code, it still occurs and has been the root cause of corrosion problems. For example, steel pipe and copper pipe are commonly used in the same installations, such as large commercial chilled water systems, hydronic heating systems, and indirect water heating systems. Copper must be connected to steel with a dielectric union. Breaking the electrical circuit between the steel and copper prevents galvanic corrosion and prevents the joint from failing.

Frozen Pipes

When water within a closed piping system freezes, the water expands. The expansion in a closed piping system can significantly increase the pressure within the piping system, and can cause the sidewall of pipe or fittings to rupture. As the frozen water thaws, the flow is no longer obstructed and water will leak from the opening. This freeze – burst – flood condition is preventable.

Plumbing codes, National Fire Protection Association (NFPA) standards, product installation manuals, and other piping installation standards address freeze protection. A reasonable designer, engineer, or installer can obtain guidance and direction as to how to prevent a pipe, valve, or other piping appurtenance from being frozen by cold weather.

For more information on Frozen Pipes, see our article on Frozen & Burst Pipe Investigations.

T&p Valve Not Piped Appropriately

Every water heater in a closed piping system is required to have a temperature and pressure relief valve (T&P). These valves are a safety device and are intended to prevent the water heater from bursting. The T&P valve opens when the water in the tank becomes either too hot or the system becomes over pressurized. The valve must be piped to an appropriate location, such as a drain or outside of the building. Defective installations can cause water damage if the valve opens and the water floods a room or building as opposed to being safely piped to a drain.

Plumbing Failure Investigations

There are a wide variety of plumbing product defects and installation defects that can cause a failure and subsequent property damage. Commercial buildings, residential properties, and factories are full of plumbing and piping systems, making the number of potential failure modes almost infinite. The mechanical engineers and building systems experts at Robson Forensic are frequently retained to investigate the cause of such failures in cases of property damage and economic loss.

For more information contact the author of this article or visit our plumbing engineering practice page.

Featured Expert

Stanley Jaworski, Mechanical Engineer & Building Systems Expert

Stanley Jaworski, P.E., C.F.E.I., C.V.F.I.

Mechanical Engineer & Building Systems Expert
Stanley Jaworski is a mechanical engineer with a broad base of professional and vocational experience; his background includes more than ten years of engineering experience involving HVAC and… read more.


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