I have a three prong dryer plug on a 30 amp breaker. The cable wired to it contains 2 conductors and a bare wire. My understanding is that the two conductors are both hot and that the bare wire is a neutral/ground (combined). Modern 4 prong outlets include separate neutral and EGC wires. To convert to a 4 prong, would it be code compliant to run an EGC from a nearby large EGC conductor (might be a solid #6 attached to water pipes), and then use the bare wire in the existing cable as a neutral? Or do I have to run a new line? I am trying to wire up a plug for electric car charging.