Posted by: nedpelger | December 24, 2008

The Mystery of Frozen Water Pipes

Dereck was right and I was wrong. There, I’ve said it and settled my bet with Construction Supervisor Dereck Hench about a recent fiasco. We had several sprinkler pipes freeze, break and leak on an apartment project with this recent cold weather. As Dereck and I and several others evaluated the installation and tried to understand what we need to change, I mentioned that pipes don’t break when they freeze, but when they thaw and expand.

Dereck told me that pipes burst when they freeze. I patiently explained that everything contracts with cold and expands with heat. Dereck asked why a gallon jug in the freezer expands and blows out the sides of the container? I knew that phenomena was true, but couldn’t think of an explanation for how it fit into my theory.

Abner, an Amish carpenter who works for Dereck agreed with me, so we both took turns abusing Dereck for being so confident and so wrong. When Dereck told Abner he’d buy him lunch for a week if Dereck was wrong, I started to lose my sureness.

And sure enough, a quick internet search teaches me that water uniquely expands when it freezes.  The water molecules line up differently as the water freezes and have more open space between, creating a volume increase of about 9%. Dereck was right and I was wrong.

So what was our sprinkler pipe problem? We needed to have a dry pendent sprinkler head poking out onto the balcony which creates a challenging situation (breaking the basic rule of keeping water lines away from exterior walls).  We determined that the insulation needs to be done extremely carefully in this area and not be allowed to be moved prior to drywall. Our exact fix will involve spaying expanded foam insulation on the sprinkler pipe in the exterior wall to guarantee that the insulation remains exactly where we need it.


  1. Reminds me of a “discussion” I had with an old roommate over which froze faster, cold or hot water

    Answer is hot water freezes faster, it’s known as the Mpemba effect

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