[Black Agnes]

What a great idea.

I’ve considered putting bricks/riprap in there for the same purpose but the water bottles are probably much better for that purpose.

[JRandomFreeper]

It was certainly easier for me to do the heat transfer calculations, since water is a pretty standard engineering material, and other things like bricks can vary widely on heat transfer characteristics.

Problems in life are engineering solution opportunities, and I've got a junk pile. ;)

/johnny