In the US, we commonly have three prongs for our electrical devices. Two of these deliver the AC Current, being both positive and negative over time and a third which goes to Ground. This is a safety thing. Whenever there is an electrical short, a static build up, or even a lightning strike, we want to divert that somewhere safe. The safest place for these excess charges is straight to the Earth, the ground below us. As big as the Earth is, it basically has an absurdly powerful negative charge. You can disperse power into the ground and it’ll dissipate safely.
Getting to Ground
It is essential for every electrical and metal component of a building to be grounded. This can be a real nightmare to actually implement. You need something that is going everywhere in the building. On the one hand, you could run additional conductors, miles and miles of additional conductors, or you use the one conductor that’s already there: the water pipes.
That’s right, older buildings ran their electrical grounds straight to the plumbing. On the one hand, this does kind of work. The copper pipes in most buildings are excellent conductors. These pipes are going to make contact with the ground at some point. If there’s a well, the pipes are going deep underground. If there’s municpal water, they’re still going to be several feet below the surface before long.
For the early days of electrified homes, it made sense. Overtime however, grounding to the plumbing has revealed numerous faults and been made illegal by most building codes.
Electricity and Plumbing Don’t Mix
Early grounding was done to the plumbing because it was easy to get to and saved time. Unfortunately, this also makes plumbing a horrendous thing to ground to: it’s easy to get to. Try to go a day without touching something in contact with the plumbing. The faucets on the sink, clothes washers, heating equipment, garden hoses, and much more for some installations. Whatever charge gets into the plumbing is going to be at risk of getting to anyone touching it.
There’s also other things in contact with the plumbing. Heating systems and the building’s own structure. In the right circumstances, high voltage in the plumbing could spark a fire or cause a small hydrogen explosion.
Water is made of three atoms: Two hydrogen atoms and one oxygen atom. As long as these atoms are happily bonded, water is basically inert and harmless. Water is an awful conductor, it is perfectly neutral without an ounce of acidity or base to it, and outside of drowning, it isn’t likely to kill. Electricity however, will break the bonds of Hydrogen and Oxygen. Separate, these are incredibly dangerous gasses. Hydrogen will catch fire and explode with oxygen, given a spark.
That’s three really big risks. On the sidelines, there’s also some simply expensive risks: ruined equipment. We use our grounding system to eat the minor electrical shorts AND the big ones like lightning strikes. Even the best, most ruggedly over engineered HVAC System is going to fall over dead if we discharge a lightning strike into it’s ground connection.
Properly Grounding a Building
Plumbing for ground has been illegal for decades in most places. The proper way to ground a building varies by the installation. For large factories with high voltage equipment, dedicated ground rods may be placed throughout the facility. Homes and small businesses will likely have three conductors running to their electrical outlets, on top of grounded junction boxes and electrical conduit to control the flow of power to the ground in a safe way.
Is Grounding THAT Big of a Deal?
It’s electricity, it can be incredibly destructive. Always plan for the worst case scenario. The worst case is pretty terrifying. To get an idea of just what a crap-ton of electricity can do, we dug up a video of 144 Million Watts, considerably less than a lightning strike, being dumped into a little iPhone. It didn’t survive.