How does water relate to the electrical industry and what you're doing? Every residence currently has interconnections between the electrical system, the telephone, the cable TV and the water system. We are all direct paths and interrelate electrically very well as conductors and paths back to ground. We must all be cooperative with one another in our actions and reactions. Please find shown in Figure 1 a basic house service, showing all of the various components and how they might be interconnected. Even when you and I both desire not to have the utilities interconnected, there is still some possibility of interconnection because basically every large appliance has directions to ground to the water pipe. We have even found instances where appliances have been grounded to gas pipes because customers do not always know the difference between gas and water pipes in their basement. It's extremely unfortunate that these circumstances can lead to some catastrophic results to the water industry in particular and I'm sure other utilities as well.
My job is to relate to you some of the potential problems. As Chairman of the External Corrosion Committee for American Water Works Association for the last 8+ years, I have seen numerous examples of stray current, created both in homes as well as industry. These stray currents are typically thought of as DC problems, but they do also occur as AC problems. We know that our pipe, particularly if it is metallic pipe, can lose approximately 20 pounds of metal per year from just one amp of current flowing on the pipeline in a path that releases the ground off of us. This is a tremendous amount of metal removal for a pipeline. On the chart (Fig. 2) we show a similar result for copper and some of the other metallic products that also could be used as a ground. This, I believe, is also a negative impact for the electrical industry in that it does not balance loads on transformers. As I'm sure most of you know much better than I, there are potential problems for you as well.
My distribution people commonly tell me of electrical shocks when they remove a meter from the water line, indicating the tremendous risk to them. It is our common practice to use grounding cables across the two pieces of water pipe before we actually remove the meters in household basements because of the risk of damage or injury to our service personnel. The appliance applications today are much more solid state electronic systems and, as shown on the graph (Figs. 3 & 4), you can see how even a small hairdryer applied to a house service can create tremendous amounts of DC component current. They do most of the controls in these appliances by the use of diodes. Again, I'm sure you gentlemen know much more about how diodes work than we do, but we have found illustrations of TV's, dimmer light switches, dusk to dawn lights, hair dryers, microwaves, large electric fans, power tools, and numerous other applications that would apply this type of modification to current wave when they are operated. Very rarely do we find the current modifications when they're in a full service loading, but again, these are currents that are not going back to you, if they flow on pipe to ground.
We know that this could have some impact on the individual privately-owned copper service lines that are in the yard of the property owner, because of corrosion to them as the current is discharged to ground from the copper service line. Although there are no studies to this effect, we do not know for sure how rapidly it would deteriorate. This is an area that still needs to be studied but we are sure this could have consequences for you as well as us through litigation of the property owners. This is one reason we've elected to make it a requirement for new service installations and have not gone back and started a retrofit program.
We are actively soliciting the NFPA to change the next revision of the National Electrical Code so it would prohibit the grounding of electrical services to water lines. We feel revision to the NEC is a much better solution to this problem. The electrical service should be grounded by direct ground rod driven at the house. Also, this would be of effect where more and more services are being retrofitted after the fact with plastic and therefore reducing the potential for grounding through this methodology. We feel that the interior piping certainly could be grounded to the rod, but all exterior piping should definitely not be part of this network. Therefore, isolation couplings and dielectric couplings are being encouraged wherever we can in the water industry to reduce the problem of corrosion in mains and deterioration of the infrastructure through the stray current problems.