$ j% c' u, V1 _$ m' _" SHot water has went through all your home's internal pipes whereas cold water comes "direct" from your local reservoir. Which should be pretty safe. / I' R' T9 o; H# e5 s9 H4 l5 X" N( E. W
Beside,furnace hot water coil is made of metal. Some of it will come into the hot water.