A long time ago, water pipes were used for grounding electrical components in the house. The idea had merit; the pipes were metal, and came to the house through the ground. Any stray voltage would be safely diverted.
Nope. Back up. Explain “Stray Voltage”.
Here’s an example; If a wire in a toaster got loose and touched the appliance, it would be “energized”. If you touched the toaster and the kitchen sink at the same time, you would have a nasty surprise.
Remember; electricity always goes back to where it came from. We have a “hot” wire, ready and waiting, behind a switch. We say, “OK, go home. But first, turn the motor on the garage door opener.” (Or go through the light bulb so I can read. Whatever.) A “short circuit” is a simple term for a connection that is a short cut around the light bulb. If you touch a hot wire, and you are touching the ground, your body provides the path for the electricity to go home without passing through the bulb.
The outside of the toaster has a green or bare metal wire attached to it. That wire is the ground wire. If a hot wire touched it, there would be a spark and/or the circuit breaker (or fuse) would open, or “blow” A blown fuse is the same thing as a tripped breaker. Electricity that tries to take a short cut is called stray, and should be directed to the ground.
So, back to the old house. The water pipe nearly always works perfectly for grounding the electrical service. Nearly. Sometimes, though, water pipes become disconnected. Maybe someone changes the floor plan, and wants a bathroom in a different room. New pipes would be installed, and the old ones would be cut off. Or maybe a section of pipe got rusty or damaged, and was replaced with PVC or PEX, which are types of plastic and don’t conduct electricity.
By the way, a better source of grounding is a ground rod, located just outside the house. Nowadays, electricians bond the ground wire to a section of rebar (reinforcing bar, used to strengthen concrete). The guy who started using that method was named Ufer. So now that kind of grounding rod is called a “Ufer”. How cool is that?
But if the water pipe is used as part of the electrical system, it must be complete. The water meter gets in the way. The solution is simple; bond a wire from the metal pipe before the meter to the pipe after. Of course, the wire has to be thick enough. Houses use 6 gauge or higher. The lower the number, the thicker the wire. It also has to be bonded with an approved connector. A home inspector would look for the presence of a jumper wire. and make sure it was firmly connected (bonded), using an approved clamp.