Forensic Analysis of a Failed Toilet Tank Fitting

Earlier this week I received a new forensic investigation assignment.  A toilet had failed over the weekend, releasing thousands of litres of water into a building.  Upon discovery of the damage, the building owner called their insurance company.  To avoid the potential for spoliation of evidence, the insured was advised by their insurer to not touch anything related to the failed toilet until I had attended the site to document the failure and completed my forensic investigation to identify the cause of the water leak. 

When I attended the site, I observed that the flexible water hose servicing the toilet tank had severed where it had connected to the underside of the toilet tank.  The connection that failed was cast of plastic and is a compression nut that secures to the underside of the toilet tank.

The Ontario Building Code regulates the application and construction of plumbing in Ontario and requires that all plumbing in a building be rated for its intended use and that it be stamped with a marking confirming that the pipe/connection/fixture is approved for use in Canada. In the event that the plumbing component is not stamped, the component is still acceptable assuming that documentation can be provided showing that the component satisfies the applicable governing codes and standards.

There are also standards that detail how plumbing is to be installed.  In this case, the plastic compression nut was required to be secured to the underside of the toilet tank by hand only (ie: not tightened with a wrench).  The application of a wrench for tightening certain types of plastic compression fittings may compromise the integrity of the fitting.   

Close inspection of the failed plastic compression fitting confirmed that no tools were used to tighten the connection however, the failure still occurred due to over-tightening.  Despite that the fitting was over-tightened, it still took 4 years after installation before the failure happened.

Subsequent to my inspection, during a "water cooler" discussion with another engineer from my firm, I was advised that he personally had caused a plastic compression fitting to fail when he tightened it by hand in an attempt to stop a slow drip on his toilet.  Just goes to show that, despite all the governing codes and standards, failures are inevitable.

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