Eh? Have it looked at by a professional. The elements are at the line voltage potential. IT's not surprising that you made an arc (you're lucky you didn't kill yourself).

If the water pipes themselves aren't at ground potential you have two problems:

1. Something bad has failed inside the unit.
2. Your system isn't bonded properly.

If the screwdriver arced while the break for the WH was off, that means the issues is elsewhere and the line for the heater was just completing the circuit.

I would check the copper pipe to ground and see the voltage potential, then switch off breakers to see what is shorted to ground (similar to the previous method).

It also seems like your house's earth ground has been disconnected. It is either a long pole hammered into the ground and jumpered, or the (cold) water pipes. If solely using the (cold) water pipes, there is likely a jumper missing someplace which is breaking the path to 'earth'.

Most likely the problem is a loose neutral at the service or a ground fault in the water heater, perhaps an element. Either one is a serious problem requiring immediate correction. The hazard to both life and property is great.