Do you need to winterize if it drops to 25°, one night but is above freezing the rest of the time during a 10-day weather forecast?

[Gary RV_Wizard]

As Tulecreeper says, there is often resistance to the ice movement that makes damage possible even if there is an opening somewhere. A fitting joint or an open valve can resist the flow of the ice enough to fracture it at that point. The strength of the surrounding walls is also a major factor - that's what happened to jymbee's bucket. The ice tried to expand in all directions, applying equal pressure. The bucket walls were simply too flimsy to resist and make the ice squeeze upward. Potable water plumbing lines are rated for much higher pressures, e.g. 160 psi for Pex water tubing.

 

[Larry N.]

As Tulecreeper says, there is often resistance to the ice movement that makes damage possible even if there is an opening somewhere.

Yes, and I suspect that the horizontal size of the container vs volume or wall height or such will matter, too. I inadvertently left a plastic rain gauge out all winter, and by spring it had cracked near the bottom. But we've had things such as flower pots sit out without breakage.