That same thing just happened here in a house I inspected this week. They have an air handler and humidifier in the attic, and something froze in the winter time and caused a big problem. I told my client I would remove the humidifier or disconnect it if it were up to me. I don't know what he'll end up doing with it.

I could see the traps freezing, but there should be enough room for expansion so that the pipes don't crack, or at least I hope so.

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Jim Robinson
New Mexico, USA