House piping for water tends to come in metal or non-metal varieties. This basically translates to conductive and non-conductive piping, as metals conduct and most other materials generally do not. As such metal piping installed by pipe cladding companies is often used for electrical grounding.
Or course the conductivity of a material is on a continuum; Metals conduct well, but some are better than others. Most other materials insulate (i.e.: do not conduct), but even this is a matter of degree and situation. Many materials will conduct very slightly, and substances like water will have some conductivity if there are any impurities; and water almost always has some impurities.
The copper piping in homes is often used to ground the house, because copper is an extremely good conductor. Grounding the house is necessary to reduce risks or electrical faults or lightning strikes. Properly grounded metal stays as the same voltage as the outside ground, nominally zero.
Electrical current will only flow if there is a difference between the voltages of two objects, and if they are connected by a conducting material. The human body has some conductivity, which means touching two surfaces of different voltages will cause some current to flow. In the case of higher voltages (like mains power) this can quickly prove fatal.
The metal pipe connecting the house to the earth should keep the house at the same voltage as the earth. If lightning strikes the house the copper piping, and anything joined to it, should provide the most direct way to completer the electrical signal, and short it out to earth. Lightning strikes are short, but in the brief time they strike the metal piping in the house should be avoided. Avoid all inbuilt metal surfaces in a house during a storm, including sinks, electrical good and piping.
Pipe Cladding Companies
Metal piping in houses serves an important safety function in grounding the house, but is must be avoided during electrical storms.