Freezing Weather and Water Jackets!
If you heat water with your woodstove, you need to be aware of the potentially explosive force of steam - if water heated in the jacket has nowhere to go, it can explode with the force of dynamite! Here's a compelling example from Gabriola:
As Karl points out: "This is the reason there has to be pressure relief valves at the stove."
(I had always thought we were safe with pressure relief values at the tank, but having one at the stove sure seems like a sensible idea now!)