Not a gret idea. $ D$ M& [7 L9 `( r/ {6 y2 r - G6 a, E' f# K9 q5 u. c% s; GHot water has went through all your home's internal pipes whereas cold water comes "direct" from your local reservoir. Which should be pretty safe. 6 H" n' ^6 W: M: ~4 G6 T; I( Z* v2 Z& J; [. ?: m
Beside,furnace hot water coil is made of metal. Some of it will come into the hot water.