Household receptacle - For a 2-wire, can I tap the adjacent bond for grounding?
They changed the rules in 2014 to greatly liberalize the rules for Retrofitting Grounds. 

They did NOT include using water and gas pipes as a substitute for electrical wires.  

However, they did allow pulling ground off the Grounding Electrode System, which does include bonds to a water pipe.  So you can bond to the wire, not the pipe.  A split-bolt connector is an easy way to tap a fat bare ground wire.