Sparking Ground Wire

I'm guessing here, but if your home has low humidity it could be static electricity.

Something is very wrong. Your electrical panel should be grounded to a ground rod somewhere. Depending on a cold water pipe for ground is not safe. I assume you have an older home. Current does flow to ground. Without ground you can not have a complete circuit.

Agree you have some kind of serious problem, within either the house wiring or something plugged into your load. Water pipes are a dangerous place from which to take a safety ground, although many older homes were done this way. Telco used to do that too but they know better now. A local lightning strike could light up someone washing their hands, in the shower, or doing dishes!