The hot and cold water pipes should be bonded.
“Bonding”* ****is connecting any metallic pipe that may become energized and must be bonded (to ground). *****Bonding is generally done by connecting a “jumper” wire across the water pipes. *****Often water heaters are installed with di-electric unions which breaks any grounding path through the heater. *Bonding all piping and metal air ducts within the premises will provide additional safety. Any metallic gas lines should also be bonded for safety. ********