I have been subject to mild electric shocks in my bathroom for years. It's probably a good time to figure out the problem (I'm still here), so I have check the voltage across the shower valve and the drain (drain is cast iron throughout house.) When the meter is set to ac, it reads 24 volts. When set to dc, it read either +11 or -11 depending on lead used. I then shut off the main breaker, and disconnected the cable line from the house. (We have no hard wired telephone line in the house - it was disconnected at the pole) I unplugged the only ups system in the house. Voltages remain the same! I check it other locations in the house - and even tried a copper pipe to a screw driver pushed into the earth - and found the same issue. The main panel is grounded the the copper piping and a ground rod that appears to be driven horizontally through the foundation wall about 6 feet below grade. Any ideas? Chris
Sounds like you have an improperly bonded neutral somewhere. If it isn't easily identified at the main service panel, you'll want to do a couple of things:
- Call your electrical company and request (or if necessary demand) that they check to make sure the incoming neutral wire is grounded correctly on their side of the service.
- Make sure that the water service to the house has a grounding connection to the ground bus of the panel within 5 feet of entering the house and before the meter.
- Install new grounding rods to ensure that they are providing an adequate ground.
- Install jumpers around any dielectric connections in the plumbing.
If none of these steps solves the issue, I'd start opening things up and make sure that you don't have a crossed neutral and ground somewhere in the house.
Check your earthing system and see if the system is perfect. Due to aging factors the earthing plate or rod would have been rusted and disconnected from the network. Even in some cases the wires running down to the plates would have damaged. Do check it once and confirm that no problem exist with the earthing system.
You or a neighbor, or the city, or the electrical utility, likely have a severe electrical ground fault btw, which is dumping massive amounts of energy into the Earth. This might kill someone. Or it might not.
This is happening in a location that is NOT directly in between your sewer and water hookups. So its voltage gradient creates unequal AC voltage between them. One other possible source could be if the soil in your area was particularly acidic or salty, and was acting as a battery between the dissimilar metals of your water supply and sewer line. This could account for the DC component. So you might have two seperate sources of stray voltage. Congrats.
If there is constant voltage between your supply and your drain, then one or both of them are not properly grounded to your electrical service panel.
Add grounding from each to your electrical service panel's ground.
Or, install some nice 24v LED lighting in your shower and power it from the drain and shower valve. Free Electricity!
Also worth noting. If there is DC voltage between your sewer line, and your water supply (caused by the soil acting as a battery between dissimilar metals) and if you "fix" that by grounding the two to the same point, or bonding them together, you will cause your sewer or water lines to corrode and break down in the ground. (cathodization and annodization) You should consider instead to electrically insulate them with a stretch of pex water supply line, and pvc sewer line just inside your basement where they enter your house. Do your electrical bonding on the house side of these insulators, not the utility side.