Not a gret idea. " [/ r7 J- r7 n& b' _ 1 [7 j8 j3 h& S) GHot water has went through all your home's internal pipes whereas cold water comes "direct" from your local reservoir. Which should be pretty safe. + ~6 N5 I& k6 \ % J9 f& V$ X) ?% ?Beside,furnace hot water coil is made of metal. Some of it will come into the hot water.