Why Frozen Pipes Burst Where There Is No Ice

It opens on a live search phrase. YouTube autocomplete carries both "why do pipes burst" and "why do frozen pipes burst", and the second half of the title is the contradiction the whole video rests on. Backup, if impressions look flat after a week: ``` A Frozen Pipe Does Not Split Where The Ice Is. Here Is Where It Splits. ``` --- Description ``` Everyone pictures the same thing: ice forming inside a pipe, swelling, pushing outward until the metal gives up. That is not what happens. In most burst pipes the crack is not at the ice at all. It is somewhere warmer, sometimes a long way from anything frozen. This is the mechanism, start to finish. How an ice plug forms at one cold spot. Why the water upstream of it is safe and the water downstream is not. What happens when a substance that refuses to compress gets squeezed anyway. Why the pipe stays silent after it splits, and why the flood arrives days later during the thaw. Then the advice everyone has heard. Leaving a tap dripping does work, and the reason usually given for it is wrong. Moving water freezes perfectly well. Rivers freeze. The drip works for a completely different reason. Ends with what actually prevents this, and what to do in the moment you find a pipe already frozen. 00:00 What everyone pictures 01:02 Where a pipe actually freezes 01:15 How the plug forms 01:52 The column with nowhere to go 02:30 The pressure, measured 03:15 Where it actually splits 03:50 Why nothing happens 04:25 The dripping tap, and the wrong reason 05:43 Copper, plastic and steel fail differently 06:58 What actually prevents it 08:09 If it is already frozen 08:34 The chain, start to finish Sources: Building Research Council, University of Illinois, for the pressure measurements and the open-tap finding. Standard values for water expansion on freezing and for residential supply pressure. ``` Timecodes come from cuts.txt, which is built from the real pauses in the narration. They do not need checking by hand.