# N$ k% ]. e/ I+ T) y& Q cHot water has went through all your home's internal pipes whereas cold water comes "direct" from your local reservoir. Which should be pretty safe.% i2 }/ _4 Z0 S1 @
* c" v1 g2 j+ Y ] QBeside,furnace hot water coil is made of metal. Some of it will come into the hot water.