Not a gret idea. $ Z7 B g( O) d+ N1 k, p ?& Y1 W1 W6 U& K: V6 v
Hot water has went through all your home's internal pipes whereas cold water comes "direct" from your local reservoir. Which should be pretty safe. ; L# x. V# s- \( X' ]: I5 x% n/ { M$ V, h
Beside,furnace hot water coil is made of metal. Some of it will come into the hot water.