Plumbing – What can cause a never-frozen indoor copper drain pipe to crack

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The 1-1/2" copper waste pipe than runs from our kitchen just up and cracked two days ago along its length, and for no apparent reason.

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The crack is in a section of pipe that runs vertically through the kitchen floor down into the basement, where it connects to an angled length of pipe (two 45-degree elbows) and then a section of pipe that connects to cast iron sewer pipe (lead and oakum seal).

diagram

I would venture to say that this cracked pipe is from the 1970s (when former owners remodeled the kitchen) and that the section of copper pipe (which didn't crack) going into the cast iron hub dates from around 1948-49, when the house was built.

Could the crack have been the result of twisting forces when the pipe connection was made to the garbage disposal beneath the sink? Or does copper waste pipe just eventually give out, perhaps because of corrosion over a period of 50 years?

Best Answer

I would inspect the entire property for more such pipe and replace any that was found. That's almost certainly a manufacturing defect and likely to be pending failure wherever that batch of pipe was used.

That is not a natural crack, nor a corrosion crack, it's too straight and uniform.

Typical "natural" cracks look like:

   expensive and stiff "sprinkler hose"


Possible ways it could have formed:

  • There was a defect/contamination in the extrusion die for that batch of pipe, propagating weakness down the length of pipe as it was extruded.
  • The pipe was rolled rather than extruded and then poorly joined (trying to make it look seamless).
  • Something/someone else uniformly scored the length of the pipe before it was installed.

Then after some years of thermal cycles and possibly mild corrosion, a crack formed and rapidly propagated along the rest of the weak line.

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