Current felt when taking a shower

[delfadelfa]

I got a call about a tenant feeling current when taking a shower. It's a 3rd floor apartment in a 100 year old house. Two months ago the plumbers removed the cast iron stack in the building because it was leaking all over the place.

I tested voltage between the brass tub drain and the faucet - 45 volts.
I tested voltage between the sink chrome stopper, which has a PVC trap, and the faucet - 85 volts.
I found an access panel where I could see some of the remaining cast iron drain pipe and the hot and cold water lines. I tested the voltage between the cast iron and the water lines - 101 volts. I had my arm against the the cast iron drain when I was testing it and could feel a tingle when I touched the water lines.

I ground clamped the hot and cold water lines, and cast iron drain lines and ran #6 copper between them.
Tested faucet to drain in the sink and tub, now the voltage is zero.
Is there anything else I should do or does this sound like I solved the problem?
Do you think replacing the cast iron with PVC caused the problem?
In the sink drain that had a PVC trap I guess there was enough water or slime in the pipe to conduct the voltage from the cast iron to the chrome stopper.

 

[GoldDigger]

I got a call about a tenant feeling current when taking a shower. It's a 3rd floor apartment in a 100 year old house. Two months ago the plumbers removed the cast iron stack in the building because it was leaking all over the place.

I tested voltage between the brass tub drain and the faucet - 45 volts.
I tested voltage between the sink chrome stopper, which has a PVC trap, and the faucet - 85 volts.
I found an access panel where I could see some of the remaining cast iron drain pipe and the hot and cold water lines. I tested the voltage between the cast iron and the water lines - 101 volts. I had my arm against the the cast iron drain when I was testing it and could feel a tingle when I touched the water lines.

I ground clamped the hot and cold water lines, and cast iron drain lines and ran #6 copper between them.
Tested faucet to drain in the sink and tub, now the voltage is zero.
Is there anything else I should do or does this sound like I solved the problem?
Do you think replacing the cast iron with PVC caused the problem?
In the sink drain that had a PVC trap I guess there was enough water or slime in the pipe to conduct the voltage from the cast iron to the chrome stopper.

If, before you bonded the remaining cast iron, there was not just a voltage (101 volts) but the ability to provide a significant current (milliamps), then either the pipe is picking up a high voltage from gradients in the local earth potential under the building, conducted to it by some other part of the piping or structure, or there is something which is leaking current into the drain system.
By bonding the pipe you have removed the symptom effectively, until such time as somebody puts in another section of PVC pipe in the wrong place, but you have not identified the underlying cause of the problem.
Whether you do more or not would, I guess, be up to the landlord and his concern about injury or lawsuits in the future.
I would also be more comfortable confirming whether the variation from earth ground was in the drain piping or the water piping in the first place.
PS: There has been, I believe, a multi-million dollar judgement in favor of a tenant in San Diego whose health was affected by this sort of current leakage.

 

[fisherelectric]

Maybe you should try turning the breakers off one at a time in order to find out if a particular circuit is causing the potential on the water or drain lines. If you can narrow it down to a particular circuit you may find you can resolve the problem.
I have a friend who was getting 3 volts on a shower drain in the concrete slab of his home. Couldn't make it go away. Pulled the meter and it still wouldn't go away. Called the power company and they worked on it for a couple days. He was at the end of the line with no neighbors nearby. They eventually told him to use a rubber shower mat and not to worry about it. He doesn't use that shower anymore.

 

[ptonsparky]

You masked the problem but did not solve it. Time to go back if you can. The breaker suggestion is a good start.

 

[Smart $]

Problem needs to be identified and resolved... but not necessarily by you. You discovered there is a problem. Your responsibility ends at notifying property owner and AHJ. Do so via phone call or such, but follow up in writing w/copies. The preceding does not preclude your services being retained to remedy the problem.

 

[ptonsparky]

Problem needs to be identified and resolved... but not necessarily by you. You discovered there is a problem. Your responsibility ends at notifying property owner and AHJ. Do so via phone call or such, but follow up in writing w/copies. The preceding does not preclude your services being retained to remedy the problem.

In short, CYA with paper.

Keep copies.

 

[electricguy61]

Does the place have an electric water heater? Might be a good place to start.

When turning off breakers to find the problem, I would turn off all the breakers, and turn them on one at a time, keeping in mind it the problem may be "fed" by more then one circuit.

 

[mwm1752]

Ther might be an issue with the grounded conductor of the service lateral. have the POCO investigate or also make sure the service grounding & bonding is properly done.

 

[ggunn]

There might be an issue with the grounded conductor of the service lateral. have the POCO investigate or also make sure the service grounding & bonding is properly done.

A wood frame rent house I lived in once had an aluminum framed window over the tub/shower. If you were standing in water in the shower and touched the windowframe you would get a significant shock. I measured 120VAC between the windowframe and the tub spigot.

 

[ptonsparky]

An older home we worked on had K&T wiring. Blown in cellulose insulation. The roof & windows leaked enough that the insulation in walls would get wet after rain along with the K&T. This would result in the metal storm doors becoming energized. Interesting find. The local FD used it for practice a few months later.

 

[mwm1752]

I once had voltage present on a floor drain in a earth floor/straw bail home -- the owner wanted to be off the grid and the batteries were to be charged by a small generator if the solar could not keep up -- the PV installed decided to feed the entire home for use prior to PV installation with the generator using a 14 ga cord that traveled past 100' -- My thought was that the grounded conductor being so small was not able to return current properly to the power source therefore creating a stray voltage to earth as part of the return. I do know that once the proper sizing of conductors were installed and the pv was operational the problem ceased. I still wonder if my hypothesis was correct or not.

 

[kwired]

I once had voltage present on a floor drain in a earth floor/straw bail home -- the owner wanted to be off the grid and the batteries were to be charged by a small generator if the solar could not keep up -- the PV installed decided to feed the entire home for use prior to PV installation with the generator using a 14 ga cord that traveled past 100' -- My thought was that the grounded conductor being so small was not able to return current properly to the power source therefore creating a stray voltage to earth as part of the return. I do know that once the proper sizing of conductors were installed and the pv was operational the problem ceased. I still wonder if my hypothesis was correct or not.

Was that grounded conductor "earthed" anywhere or isolated? If isolated and it can not return enough current then the load just sees a voltage drop. If it is earthed, then you allow current to flow through any path it can find.

To the OP, you need to measure to a probe in the ground that is isolated from the building electrical grounding system, to determine what is operating above ground potential, and then work from there. You could have an object connected to an ungrounded conductor, inadequate bonding of either the water piping or the cast iron drain piping, a service neutral conductor with a high resistance in it somewhere, or even just voltage drop across a good conductor, but probably not that likely with the amount of voltage you are measuring. You can even have voltage drop originating in the POCO primary neutral.

Removal of a section of the cast iron drain pipe likely removed any bond you did have between it and the water piping, the water piping is likely bonded to the electrical system, but seems like metal drain piping often is not and if it is running into the ground is an electrode and your electrical system and everything bonded to it is operating at an elevated voltage either from simple voltage drop or because of a high impedance in the grounded conductor.

 

[mwm1752]

The grounded conductor being tied to the electrode system would be the connection to earth

 

[kwired]

I once had voltage present on a floor drain in a earth floor/straw bail home -- the owner wanted to be off the grid and the batteries were to be charged by a small generator if the solar could not keep up -- the PV installed decided to feed the entire home for use prior to PV installation with the generator using a 14 ga cord that traveled past 100' -- My thought was that the grounded conductor being so small was not able to return current properly to the power source therefore creating a stray voltage to earth as part of the return. I do know that once the proper sizing of conductors were installed and the pv was operational the problem ceased. I still wonder if my hypothesis was correct or not.

The grounded conductor being tied to the electrode system would be the connection to earth

Let me rephrase that, was the grounded conductor earthed and bonded to equipment at the source only?

If it was also earthed/bonded at the load end then you create parallel current paths through exposed conductive objects. If the grounded conductor remains insulated beyond the source you will have a voltage between it and ground at the load end but since it is insulated you are not under normal circumstances exposed to this voltage just like you are not exposed to any voltage from any ungrounded conductors as long as they remain insulated.

 

[CONDUIT]

An older home we worked on had K&T wiring. Blown in cellulose insulation. The roof & windows leaked enough that the insulation in walls would get wet after rain along with the K&T. This would result in the metal storm doors becoming energized. Interesting find. The local FD used it for practice a few months later.

I had a similar situation before. It was caused by an open neutral on the utility side!

 

[kwired]

I had similar situation to the OP before but there was no recent plumbing changes. There was a cast iron drain system and metal water piping. The water piping was bonded to the electrical system but the drain piping was not.

This voltage started appearing after a ice storm downed a lot of lines in the area and was going to take months to repair all the damages. POCO's had many primary neutral conductors laying on the ground still in operation. They claimed this would not cause such problems. I disagree. In general they were correct that their system will work, but open circuit conditions in their MGN will create somewhat low voltage gradients in places and this happened to be one of them. The customers service neutral is bonded to the POCO MGN neutral, so it is effectively still the same conductor and so is the water piping that is bonded to it. The unbonded drain pipe however was also buried in the earth and was at true earth potential. Any voltage drop between the MGN and true earth will exist between those two points.

In my case I bonded the drain piping and figured it needed bonded anyway and the source of the voltage at that point in time would be cleared up whenever they got around to fixing their downed neutral lines. At that point restoring as many services as quickly as possible had much higher priority than repairing down MGN conductors.