[cameron_b]

just at face value though, the inefficiency of thermal transfer would make a sufficient buffer to prevent the freezer from taking too much load from the volume of water.

25' of copper would not be nearly enough to do the whole job but it would lower the temp some, and over time it would lower the temperature relatively safely ( safe against freezing the lines ) and likely consistently unless the tub is continuously filled with mammals or in sunlight or sunlight-warmed air.