Not a gret idea. , @3 m8 W9 Z$ X( y, \& O" k. \ 6 Z8 Q: e9 `, `+ d4 m9 `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. 9 s ^0 Q8 s+ e/ L( n0 i3 T) x4 i" g 4 e7 i1 i% _ I" LBeside,furnace hot water coil is made of metal. Some of it will come into the hot water.