Technically all metal piping in a house is supposed to be bonded together to form one big grid. This way there will be no stray voltage running around. However here in NJ, the gas company does NOT WANT us to bond to the gas piping. The state feels that there are several connections amongest the gas appliances to have enough bonding through the regular wiring. For example the ground wire on a plug of a gas dryer, or the plug of a gas stove, furnace, boiler, etc. The state feels that there are enough connections between the gas piping and the grounded conductor.
Harold
