Not a gret idea. 4 m9 F% ?* \; u; P; _ ( `5 N1 y) K+ Q# Z' T- M0 WHot water has went through all your home's internal pipes whereas cold water comes "direct" from your local reservoir. Which should be pretty safe. ! V. w. m% \! ^# z; Q- B+ S/ O4 K9 Q; h+ {1 s2 v4 k& \8 S7 Z, F
Beside,furnace hot water coil is made of metal. Some of it will come into the hot water.