Imploded Water Bottles

I left store bought and factory sealed plastic bottles of water over the winter at my cottage. The water inside the bottles would have frozen solid over the winter. In the spring they are all back to liquid water again but have imploded. Why? Thanks
- jane (age 37)
Canada

Here's a guess. The water froze and expanded. Although the shape of the bottle can change and it can stretch and expand a little, that may still leave a high pressure (above atmospheric) inside. Perhaps that pressure difference was enough to create a little air leak, although the bottle was supposed to be sealed. Then when the water melted there would be reduced pressure (below atmospheric) inside. It's easy for the sides to cave in (implode)  to get rid of that pressure difference, so it never got big enough to reverse the leak.

Mike W.

(published on 05/15/2018)