[Cob] cob/earth oven also heating hot tub intake?

[KC Chandler]

 From: Tys Sniffen 
[ I would like to build a cob baking oven and run copper piping through it,]

You can purchase stove coils of almost any maleable metal (obviously not iron). My preferance would be stainless steel... for strength and in the eventuality that you may want your water potable.
 
~KC