" J2 U4 T0 G/ f8 DHot water has went through all your home's internal pipes whereas cold water comes "direct" from your local reservoir. Which should be pretty safe. + j% S0 A+ p% U4 o1 H1 x+ x7 c @: o2 r' R' D8 m% H
Beside,furnace hot water coil is made of metal. Some of it will come into the hot water.