A Small Water Line Leads to a Large Loss


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    • Failure Analysis
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    • Machinery Damage & Assessment

A large oceanfront house was custom built after two years of planning and construction.  The house had three stories over an elevated foundation.  Shortly after the house was completed, the owners arrived one evening and found water pouring from above when they parked in the garage beneath the living spaces.  

The owners quickly traced the water source to a third story bathroom toilet and closed the cut off valve to the toilet.  By that time, the water had drained from the bathroom to the second story through recessed can lights over an heirloom grand piano, filling the piano with water that then spread throughout the lower stories of the house.  This turned into a devastating loss for the owners because their heirlooms were destroyed and their dream house had been made unlivable.

The water leak at the third story toilet came from a toilet water supply line that had fractured at the connection to the toilet.  The engineering assignment was to determine the cause of the water supply line connection fracture.

Toilet supply line as installed.

Toilet supply line as installed.

The water supply line appeared to be robust, with a braided stainless steel exterior.  However, the water supply line was ten inches long in the six inch space between the toilet cut off valve and the toilet connection, resulting in two sharp bends between the cut off valve and the toilet that caused significant stress on the fittings on both sides of the water line.

Fractured toilet connection. Wrench marks are visible on the fitting.

Fractured toilet connection. Wrench marks are  visible on the fitting.

Additionally, although the water line toilet supply plastic fitting was clearly marked ‘hand tighten only’ on the toilet end, there were wrench marks on the fitting that were consistent with over tightening at installation. These marks were located in the area where the line fractured.

Visual and microscopic examination showed that the water supply line fractured as a result of excessive stresses at the plastic toilet connection.  Plastic materials are subject to failure by ‘creep’, a well-recognized mechanism of slow fracture in plastic materials that can take up to several years.

"Hand Tight Only" warning on fractured toilet fitting.

“Hand Tight Only” warning on fractured toilet fitting.

In this case, although the toilet water line appeared to be robust and suitable for this expensive home, it was improperly sized and installed in a manner that led to the water damage.  Water supply lines are sometimes installed by the plumbing contractor, but are often installed by different subcontractors to the general contractor who set and connect appliances throughout a home after the main plumbing is complete.

John Phillips, senior consulting engineer at Warren, has more than 30 years of crane and heavy equipment experience and more than 19 years of experience in forensic engineering.    A licensed professional engineer in South Carolina, North Carolina, Georgia, Louisiana and Ohio, he’s NCEES registered both as a model engineer and with The United States Council for International Engineering Practice, USCIEP. John has designed crane systems, supervised installation, tested and certified lifting equipment even serving as a project engineer for maintenance and certification of nuclear weapon lifting and handling systems. John is a certified fire and explosion investigator and fire and explosion investigator instructor by the National Association of Fire Investigators. John is a member of the American Society of Materials and American Society of Testing and Materials, as well as a voting member of ASTM Ships & Marine Forensic Sciences, Forensic Engineering, and Performance of Buildings committees. 

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