I work as a plumber, I often visited apartments to replace plumbing fixtures, namely faucets, toilets, strapping. I had to change metal pipes to plastic ones. So in the process of this activity, sometimes the tenants of the apartments asked the question what kind of wire goes from the floor and ceiling and why is it needed.
Especially this question worried those who were engaged in repairs in the bathrooms. They almost always wanted to remove it...
At one time, I had to participate in the composition of the brigade in the overhaul of houses. Namely, they changed water supply, sewerage and heating systems. Before the commissioning of the houses, the receiving commission was given a coil of single-core copper wire, with a cross section of 3-4 mm and we had to roll it out from the last floor of the house, which underwent a major overhaul, to the basement premises.
Make a ground loop in the basement according to the rules and connect to it. But as I know, sometimes shabashniki hammer a used pipe, which is rusty half a meter into the ground with a welded bolt. Naturally, it is impossible to make a contour like that, but usually they had their "own" selection committee
A copper conductor coming from the apartments was screwed to the ground loop on a bolt. In bathrooms, this wire was lengthened, often on twists, which is not correct, it is necessary on threaded connections and was brought to metal baths. They have a special eyelet for screwing the wire.
If the bathtub is acrylic, then the wire was connected to the metal frame.
I was always interested in the moment, but is it possible to operate a metal bath without grounding? In those days, I decided to conduct an educational program at the local ZhEKovsky electrician, to find out whether these manipulations with "extra wires" are necessary? To which he did not give a clear answer... The only thing, he said, is that under certain conditions, grounding appliances in the bathroom is a good thing, and in some circumstances it is evil.
But according to the "Electrician's Bible" namely RULES FOR THE DEVICE OF ELECTRICAL INSTALLATIONS (PUE). Edition 7
It is necessary to make a potential equalization system in Bathrooms and toilets:
Namely, cold water and hot water risers, a sewer pipe, a bathtub, and a gas pipe are connected to the common grounding bus. This rule has come to us since the days of the USSR. Such manipulations allow you to protect people from electric shock, when it leaks through a water heater, washing and drying machine, etc.
Therefore, in no case should this wire be removed from your toilet. If you nevertheless remove it, then you leave higher apartments without grounding. Thus, you endanger the tenants above you.