what is the purpose of a copper wire clamped to a water line?
This has nothing to do with earthing. The purpose of Earthing cables is in the event of a fault to allow a large enough fault current (Yes, we actually try and generate as much fault current as we can on purpose) so the safety device (fuse, mcb, etc) can be operated fast as possible. The cable on you pipe is called Equipotential Bonding. The purpose is to make all extraneous metal parts (metals things which are not normally live but may become live if a fault develops) at equal potential. (in simple terms equal voltage) Say you had a metal sink and a metal cooker. The cooker has a fault on it and the case becomes live. If it is already connected to the sink through bonding they will all then be at the same voltage (potential) and therefore it will not be possible to receive an electric shock. If the sink was not bonded you would probably have a direct connection though it to earth giving a large voltage difference from the cooker through you to the sink and earth resulting in a shock.
Technically - particular the copper line could artwork nicely adequate. Legally - no, copper line won't meet code for grounding an electric powered circuit. bypass to a ironmongery shop and get a grounding rod and an acorn nut. power the rod into the floor (i recognize they are very long and that's going to be much of attempt to get the completed ingredient pushed down, reckoning on the soil.) Slide the acorn nut over the uncovered piece of rod, slide your floor twine interior the acorn nut and tighten it down.
It is to insure that there is no potential voltage from the ground established at the service panel and ground reference to the water/water piping system. The water piping should find a path to ground by itself, but variances of soil quality and conductivity of piping may limit the ability for good current flow. If it is disconnected and an additional ungrounded fault develops at a locally located transformer then you could get shocked touching anything that is connected to the equipment connected by a ground prong and a water faucet. In an really old house (before the invention of plastic pipe) it may be the only ground reference. In a newer house, or if the house has been updated, a separate ground (normally ground rods or a ufer ground) should exist, the ground to a water pipe is recognized as only a supplement to a grounding electrode . Also required (but usually not present in many residential buildings) is bonding to building steel, gas, sprinkler piping, re-bar encased in concrete, and any transformers. A jumper is also required from the hot and cold side of a hot water tank or boiler.
