One striking example of plastics gone awry was the defective ABS drainpipe debacle that resulted in class action suits against various manufacturers. The manufacturers had used defective resin in ABS drainpipes widely included in residential construction in the last half of the 1980s. The defective ABS pipes broke at the joints, causing leaks in walls and under slabs. These pipes are still causing problems nationwide.

In another case, a company designed, manufactured, and marketed a faucet water-line riser made from a polymer composite hose with metal connector nuts on each end. Connecting the nuts to the hose required barbed inserts inside the hose that were held in place with metal ferrule crimps. The inserts were made using nylon 6/6 plastic, which is subject to hydrolysis in hot water, meaning that the nylon will absorb the hot water causing the long nylon polymer chains to break. Over a period of years, the nylon 6/6 becomes weak and brittle, and eventually breaks. The break causes the metal nuts to come loose from the composite hose, which results in flooding.

Published engineering texts documenting the problems with nylon 6/6, including water absorption, hydrolysis, and failure, did not deter the manufacturer from choosing a plastic that was not suited to the environment in a hot-water supply line. Failures from these nylon barbed inserts have accounted for millions of dollars in property damage.

Another type of plastic failure is the cracking of plastic coupling nuts used in water-line risers to connect toilet ball-cock valves to the right-angle standoff valves in walls. These coupling nuts are supposed to be hand-tightened only. If the installer uses a tool, such as a pair of channel locks, to tighten the nut, the nut can become over-stressed and crack. Eventually, the coupling nut will fail and hundreds of gallons of water will flow into the home.

Even if these nuts are installed correctly, some are made from polyacetal resin, which is subject to chlorine attack even at concentrations as low as one part per million. These nuts break down over a period of five to seven years and eventually fail by circumferential cracking around the base of the threads. I have analyzed dozens of such cases in which no tool marks were found, yet the nut failed anyway after five or more years of service.

Metallic Fixture Failures

Plastics are not the only materials that can fail. Modern stainless steel braided water lines are an example of a good quality material with an Achilles heel. Although stainless steel is remarkably resistant to corrosion, chlorine attacks it, causing it to corrode and become brittle. The stainless steel braided water lines rely on the braids to contain rubber hoses inside, keeping the hoses from bursting. If the braids fail, the rubber hose will fail as well, creating another water loss. These types of failures can be avoided by keeping chlorine-based cleaning products away from stainless steel water lines.

Brass plumbing fixtures are not without problems, either. Many brass castings have built-in flaws. I have examined dozens that have cracked and caused costly leaks. Examination of the fracture surface within these cracks usually reveals a bubble in the casting that weakens the brass and causes crack formation. Often, the fractures are so small and unremarkable that the installer does not notice them. Even when initially pressurized, the brass casting may not leak. It is not until the crack grows that a leak is noticeable.

Corrosion of pipes is still commonplace. Even though most modern homes include plumbing with copper pipes, these are not immune from corrosion. Dozens of copper pipes have developed pinhole leaks in crawl spaces and under slabs. These usually develop from the inside out, caused by small foreign particles in the water that settle in the copper pipes. The particles interact with the copper, causing oxygen-depleted corrosion cells to form. The cells cause pitting corrosion that, ultimately, forms a hole all the way through the pipe.

Corrosion from the outside also can occur, usually due to contact with corrosive soil. This can be avoided if the builder surrounds the pipe with free-draining gravel above the native soil or wraps the pipe with a corrosion-inhibiting coating such as plastic tape.

Water heaters corrode, as well. Usually, the tanks of water heaters are constructed of steel with glass liners adhered to the steel tanks. The glass liners serve as protective coating to inhibit corrosion. Despite the best efforts of the manufacturer, however, small holes or “holidays” occur in the glass, and areas of steel exposed by holes tend to corrode. To inhibit the corrosion, sacrificial anodes often are used inside the water heater tank to protect the steel. The anodes do not have an infinite life, however, and eventually will corrode away.

If the water heater is connected directly to a copper piping system, the steel of the tank and the copper in the pipes can set up a galvanic corrosion cell that will cause the tank of the water heater to corrode away rapidly. This always results in leaks. To prevent the galvanic corrosion from occurring, it is imperative that a dielectric coupling be used to electrically separate the steel tank from the copper pipes. Failure to use such a coupling constitutes defective installation of the water heater.

Adjusting Water Loss Claims

Defective plumbing fixtures and improper installation account for many of the water loss claims in the United States. Forensic engineers often investigate claims that arise from these defects and subrogation can be pursued successfully. Careful analysis and documentation of the evidence can present a solid and convincing claim against responsible parties, and insurance carriers can recover significant revenues.

Claim adjusters can do a great deal to document causes of water losses and help preserve evidence. For example, toilet overflows and leaks cause millions of dollars of water damage each year and, yet, many of these losses are poorly documented, resulting in the failure of the subrogation process. When faced with these claims, adjusters can take a number of steps to increase the chances of successful subrogation.

It should be determined whether the toilet overflowed from the bowl or the tank, and this information must be passed on to the forensic engineer. An overflow from the bowl indicates a clogged toilet with an accompanying leak from the tank into the bowl. A tank overflow, however, signifies a malfunctioning valve in the tank itself or the improper sizing of the tank overflow drain.

Photographic documentation is important. Several photos should be taken of the toilet in place, including the condition of the guts in the tank.

A forensic engineers should have the opportunity to inspect the entire toilet. If it is impractical to conduct the inspection in place, the toilet should be shipped to the investigator as a unit. The adjuster should not attempt to determine the cause of the failure and send only selected parts to the engineer, as this can result in a report from the engineer stating, “No conclusion is possible because insufficient evidence was available.”

When dealing with the failure of a waterline riser, the adjuster should document the waterline in place with several photographs and note the use of the waterline, as well as its age. The entire waterline should be sent to a forensic engineer, not just the failed part.

Additional questions to consider include whether the waterline was used to connect to a faucet. If so, was the connection for cold or hot water? Was the faucet in a kitchen, bar, or bathroom? It also should be ascertained who installed the waterline, and where it was purchased. In the case of a failed stainless steel braided waterline, it is useful to know whether any chlorine-based chemicals were stored near the failed waterline.

Failed washing machine hoses also need careful documentation by on-scene adjusters. These hoses usually fail right at the ferrule crimp. It is important, therefore, to check whether the hose was bent at the crimp when in use.

The age of the hose also is a factor. Had it been furnished with the washing machine? If the hose were a replacement, when was it installed and by whom?

Manufacturers often deny many hose failure claims by placing blame on improper use or installation of hoses. Careful documentation at the scene can refute these arguments.

Adjusters also can play a significant role in the investigation of water heater failures, many of which involve defective installation. In addition to documenting the installation details with several photographs, the adjuster should take close-up photos of the waterline connectors to the water heater. A forensic engineer should examine the water heater and the waterline connectors to determine whether proper dielectric couplings were used.

The insurance industry pays out millions of dollars per year in water loss claims. Because many of these are due to defective materials or defective installation, they can effectively be brought to subrogation, resulting in millions of dollars in recovery. Adjusters, working in concert with forensic engineering investigators, can play a key role in the subrogation process.

Michael J. O'Connor, P.E., is a senior engineer for EFI Global, an engineering, environmental, and fire investigation firm. He is based in California and can be reached at [email protected].