Often, the hot and cold are bonded to the panel at the water heater location.
I was thinking along the lines of,
Water heaters that rust out quickly might be connected to water pipes that are not grounded. Hot water pipes are not grounded in many homes. To get 'rid of stray current corrosion, jumper between hot and cold pipes with #6 solid copper wire. And check that cold water pipe is grounded to main panel and to grounding rod.
http://waterheatertimer.org/How-to-wire-water-heater-for-120-Volt.html
Most electricians automatically bond the cold water line but do not ensure that the cold and the hot water lines are metallically interconnected through mixing valves in the plumbing fixtures. Since Section 250.104(A) requires all water-piping systems to be bonded back to the service, and hot or cold water lines are not specifically mentioned, both hot and cold water lines must be bonded and connected back to the building service.
http://waterheatertimer.org/pdf/water_pipe_grounding.pdf
My problem is that I don't have a separate ground wire going to the cold water line (there's a copper jumper between cold and hot water pipes) and I don't have a lightening rod on the roof. (Most homes in Phoenix don't have them, just as most homes don't have gutters, and most homes have the AC on the roof. Weird, I know...) I figure the ground wire in the conduit wiring is being used to ground it. I hope there's no harm connecting the WH ground screw to the cold water pipe. (I work with electronics and fear ground loops.)
Electric water heaters have [a] ground screw. Make sure ground wire from main panel is connected to screw. Attach ground wire from both hot and cold pipes to ground screw.
ibid.
Gutters and a lightening rod are on the schedule for the future. I have no trees near my house that can attract lightening...
Now if I can only figure a way to install heat traps since my water pipes are right above the WH, so they go straight down to the WH inlet and outlet... Shark hoses aren't long enough, so I'll have to find flexible copper that is long enough. Heck, my WH doesn't even have an expansion tank...
And yes, I will be replacing the WH circuit breaker with a new one when I install my WH this weekend.