Not a gret idea. ' t2 r# v/ Y8 I: C8 F 0 _9 G# E) ~, t6 j, e4 kHot water has went through all your home's internal pipes whereas cold water comes "direct" from your local reservoir. Which should be pretty safe. / u! ], r: L5 a. ]5 T M3 A, N/ ~4 b8 x. W- R0 Q \
Beside,furnace hot water coil is made of metal. Some of it will come into the hot water.