Not a gret idea. * `; C# r4 U K" j* v. |: l$ e' H' x
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. ; d7 n, M+ Q y0 q, `- d% [ c" u2 E6 s
Beside,furnace hot water coil is made of metal. Some of it will come into the hot water.