United States and Canada

Pipe Failures in Residential Plumbing and Heating Systems


SGH investigated the cause of failures in pipes used in residential domestic hot water and hydronic heating systems in the United States and Canada.  Occurring after less than 10 yrs in service, the failures of crosslinked polyethylene-aluminum-crosslinked polyethylene (PEX-Al-PEX) pipe were characterized by blistering and splitting of the exterior pipe wall preceded by darkening and bulging of the outer PEX layer.

SGH obtained field samples for laboratory examination and testing.  Highlights include the following:

  • Observed brittle microcracking of the inner PEX layer and corrosion holes in the aluminum layer precipitating hydrostatic rupture of the outer PEX layer
  • Conducted testing focused on basic dimensional and material properties to determine if fundamental material or manufacturing defects were present
  • Determined that PEX material had low gel content (indicative of inadequate crosslinking), reducing the strength and crack resistance of the pipe
  • Identified early depletion of the antioxidant, decreasing the resistance to oxidative degradation and increasing susceptibility to early failure by wall rupture

Our findings contributed to settlement of a class action lawsuit on behalf of homeowners.

Project Summary



Completion Date
Repair & Rehabilitation
Advanced Analysis | Applied Science & Research
Infrastructure & Transportation
Merrill, Nomura & Molineux, LLP
Specialized Capabilities
Buried Infrastructure | Failure Analysis | Materials Science | Microscopy

Key team members