“Missing jumper wire at water meter” is a common electrical defect and safety hazard noted in many home inspections for older homes. The jumper wire is actually a grounding wire, a short section of large gauge wire that “jumps” or goes across the water meter and is securely attached to the water pipe at each side.
A jumper ground wire at the water meter is am important safety device that should be installed on most homes that have a buried copper or galvanized water supply line that brings water into the house. Buried metal water pipe makes a good ground for the electrical system and is commonly used for grounding the homes electrical system.
In most older homes the electrical systems are grounded from the electrical panel to the water supply line where it enters the house. This grounds the home’s water pipes throughout the house and is a good and safe practice that has been done for over a century. The grounding system in a home provides an easy path for electricity to flow to earth should a problem, such as a short circuit, occur.
This is doubly important because older homes did not use grounded wiring and it was a common practice to ground devices or attach ground wires to the copper or galvanized water pipes throughout the house. In the 1950 house pictured at left there are 4 ground wires attached to a copper pipe, on each for the washing machine, TV cable, phone line and a GCFI outlet for a bathroom. Often wires grounded to water pipes are not visible but are hidden behind walls or under floors.
Missing Jumper Wire is A Potentially Serious Safety Hazard
The water meter at left does not have a jumper wire, therefore if any of the grounded devices (from above picture) develops a short circuit or similar problem the water pipes on the house side of the meter could become energized and deliver an electrical shock to someone touching the copper or iron water pipes. This happened to me on a plumbing job years ago; I grabbed a galvanized water pipe in the ceiling of a basement and could feel the electrical current in the pipe. It was fairly mild electrical short, kind of like a tingling or numbing sensation and thank God I was able to let go. It is especially dangerous if you are standing in water the the short is more powerful. Plumbers and homeowners have been killed from this type of electrocution scenario. In some cases when your body becomes the grounding path, with strong electrical current, you can not let go of the pipe, which can result in death.
We don’t want people to take the place of jumper wires. This is why we want to fix this defect as soon as possible. Should an electrical fault occur where no ground path is present, the electrical potential is just sitting there waiting for a person to come along, touch some component of the system, and by accidentally providing a path to earth through their body, receive a burn or potentially fatal shock.
When grounding wires were attached to water pipes it was “assumed” that they were a good grounding source since the supply line to the house was buried deep in the ground. This was a common practice usually done prior to installation of water meters. The safety hazard occurs when a water meter is installed on the water supply line, they use rubber washers at each side. The insulating quality of the rubber washers disrupts or breaks the ground path from the buried water supply line to the rest of the water lines in the house. When this is the case, only the water pipe(s) on one street or earth side of the meter are grounded.
The reason water meter grounding jumper wires are missing on so many homes is the old building codes did not require them. The purpose of the electrical grounding system in a home is for safety, it provides an easy path for electricity to flow to earth should a short circuit or other problem occur.
The electrical grounding system requires a good grounding source such as a buried water supply line or a ground rod that is driven deeply into the ground made of copper or galvanized iron which are good electrical conductors. The current electrical code requires two or three sources of grounding for a home. Proper grounding allows current to flow to earth through the ground system when needed and helps assure that a circuit breakers will trip or fuses will blow should a problem occur. Proper operation of these over-current devices help prevent fire and electrical shock.
Most houses use the water supply line to provide an grounding path for the electrical system. If the ground wire from the electrical panel is attached downstream from the water meter, a jumper wire must be attached to carry electrical current past the meter. If either of the pipes attached to the water meter is nonmetallic, this grounding method cannot be used. Installing a ground jumper wire is a relatively easy task that can be completed in about 20 minutes using common hand tools.
Houses with plastic water pipes, usually those on wells, use grounding rods instead, usually two or more grounding rods or grounding sources are needed.