My own stupid electrical question / filling hole in concrete floor

[bent]

I am doing a Renovation in the basement. Where the Copper water pipe goes down vertically into the ground, the concrete floor is missing. there is a

7" trapezoidal gap in the pour. I have partially covered it with the 2x4" flat to the floor that is part of a new stud wall. but the hole still juts out. The hole sticks into what is to be a finished tiled floor I will do shortly diagonally 1.5" x 3". Then on the other side of a 2x2" partition wall the hole continues about another 6"x6". There is also the main ground wire from the fuse box screwed to the same copper water pipe about an inch above concrete level. However the bare wire low gauge crimp clip which attaches the wire to the pipe with a wrap around steel clamp and bolt is kinked right off, and I have mashed the bare twisted wire just into the main water shut off tap wheel. It is all right at the water meter.

Two questions:

1) Can I fill this hole with concrete (or how much of the hole). It is quite a noticeable gap, with nothing but dirt a few inches down. A little of this hole is on the edge of a new tile floor I'll be doing. I'd like to fill it (all) in. Is there any reason not to wrap an 1/16"- 1/8" flexible whatever around the water pipe, and fill it up.

2) What if any danger am I in handling the bare ground wire for a while to re-crimp/clamp without shutting off the main power?

[todd]

We're doing a major addition to our house which required an upgrade to our water service. After they broke out the floor, pulled the old stuff out, and put the new in, they filled the hole with concrete right up to the pipe. My little suburb here is pretty strict with the codes, so I'm sure that's fine.

Close to zero. If you're concerned about that, I'd stay out of the shower if I were you.

todd

[Locutus]

wire is harmless...

[Puckdropper]

"Locutus" wrote in news:4417bc37$0$155$ [e-mail]:

In most cases, contact with the ground wire is harmless. However, you can get shocked by it due to static electricity or unusual circumstances such as an idiot doing wiring in your house, or lightning hitting the right place. It's metal, therefore it conducts current. It has the potential to be dangerous.

Puckdropper

[RayV]

Copper and concrete are not a good mix. Many of the Levittown homes in the NE have had to change from the original copper slab heat to baseboard because of this.

From:

"As time went by, some of the copper tubing began to leak, and water would soak into the ground rather than rise up through the floor. Consequently, homeowners didn't know when a minor leak occurred, which eventually led to major problems. Both Levitt's and Wright's homes had early copper piping that pushed the envelope right to its limits in this way. If workmen operating on a tight schedule installed the piping with too much play, the pipes could easily break. In fact, the very nature of copper's interaction with concrete made corrosion of the pipes likely to happen eventually, unless a protective barrier was installed-a process that was perfected much later. Once leaks began they were nearly impossible to fix, leading many homeowners with this problem to abandon the systems and install baseboard convectors instead."

You could always trust the guys at copper.org or the thousands of people that had their system fail. I would at least wrap the pipe in a thin layer of foam to keep the concrete from touching the copper.

[chuck]

There are two issues:

Is it possible that lethal voltages might be found between the copper pipe and the grounding wire (when disconnected from the pipe, of course)? Absolutely! It is not likely, but it can and has happened.

Second issue is what to do about it? You can carefully measure the voltage when the wire is disconnected, but you need the right kind of meter for that. Best, and easiest, approach is to clip a jumper between the grounding wire and the copper pipe before removing the clamp, etc. When you're finished, remove the jumper.

Needless to say, potentially lethal voltages are a sign of a problem that ought to be diagnosed and corrected. They are not a normal condition. This is very definitely not in the same class as taking a shower!

Good luck.

Chuck

bent wrote:

[chuck]

Maybe I read too fast. To "handle" the ground wire while it is connected to ground will not be a problem. My previous post assumed you wanted to disconnect the ground wire from the copper pipe to replace the clamp. If so, it would be good to switch the main breaker off as well.

Chuck

chuck wrote:

[Bill B]

As long as the ground is still attached, zero risk. If you disconnect the ground and there is something bleeding current to ground, it will be live.

I had a "hot" computer case once. If I touched it, while touching something grounded I got a heck of a zap. Turned out the extension cord I was using had the ground broken inside of the male end of the cord. AC inducts current into nearby conductors real well, so it was loading the ground wire, no longer connected to a ground, with lots of juice. Since the case of the computer is directly connected to the ground lead... Replacing the cord solved the problem.

[Locutus]

FTR, I agree, I never let concrete touch the copper, however any reaction between the copper and concrete usually take 20-30 years..

[todd]

I don't understand your last sentence. I'm saying that if you're gravely concerned about having a "potentially lethal" voltage connected to your plumbing pipe, then I'd avoid touching any of the plumbing in the house and I certainly wouldn't get soaking wet and stand in a shower lest the voltage decide I'm a better path to ground. Is there a non-zero risk of dying from doing this? Yes, there is. So while we're at it, why don't we have the OP wear linesman's gloves and use a hot stick to install the clamp?

todd

[Steve A]

As a plumber, I have run into about 4 cases of the water bond having enough voltage to give me a good tingle when it was disconnected. We have learned to use automotive jumper cables to jumper ground wire to water service while bond clamp is being reconnected.

[Steve A]

ps: I aways install jumper before relocating a ground clamp, checking for sparks with jumper cables. I did get quite a tingle ONCE.

[Bugs]

Copper corrosion under slabs is a big problem all across the country. As a consulting engineer I made many investigations of these problems. My experience led to three basic actions to avert problems. Don't use copper water pipe as an electrical ground. The transient currents can turn the pipe to Swiss cheese. If the water supply tests for any level of hardness and CO2 [Carbon Dioxide], the stray currents will cause an electrolytic erosion of the copper, forming Copper Carbonate inside the pipe. This is easily identified by the Turquoise color of the deposit. Don't install copper pipe in soil that has been treated with salt or Copper Sulfate to inhibit weed growth. This is a common practice among subdivision developers, causing widespread leakage in new subdivisions. I won't even mention the lawsuits that these problems have generated. It is something that every prospective home buyer should check out. Bugs

[John McCoy]

Bill B wrote in news:5aydndHLo5XMvIXZRVn- [e-mail]:

Um, no. You'd need miles of wire to induct any appreciable amount of charge into a parallel unconnected wire at the frequencies power lines work at.

Something else was also connected to the ground lead - quite likely the power line neutral (the "white wire" - I'm guessing this since you've stated the extension cord was defective). As you observed, when the far end of the ground lead wasn't grounded, this provided enough charge on the case to give you a tingle.

John

[chuck]

Hello Todd,

From the way you've posed the question, I can't tell whether you understand the basic electrical concepts involved.

Let me just say that appliance ground faults are so common that a good part of the National Electrical Code (NEC) is devoted to protecting people from them. Breaking the ground connection exposes one to the very dangers that the ground connection was installed to protect against.

Taking a shower is just not equivalent to removing the protection against appliance ground faults that the NEC requires.

There is no electrical safety risk in taking a shower UNLESS there has been a grossly egregious wiring situation that would at a minimum violate the NEC and could be grounds for criminal negligence. I would not (and have not) advise everyone to call in an electrician before taking a shower. But I will advise everyone who wants to break his ground connection to be careful.

I agree with the notion that no part of our existence is without some risk. Rationality therefore means we expend efforts to avoid a risk commensurate with the risk's probability. I think advising the OP to be damned careful when removing the protection required by the NEC because without that protection you might die goes well beyond the simple truism that nothing is without risk.

Does that clarify my statement?

Chuck

todd wrote:

[Sailaway]

Steve A wrote: >As a plumber, I have run into about 4 cases of the water bond having >enough voltage to give me a good tingle when it was disconnected. We >have learned to use automotive jumper cables to jumper ground wire to >water service while bond clamp is being reconnected.

Without going into great detail: You have to remember that wire - ALL wire - has resistance. So when you disconnect one, then current will take the path of least resistance to ground. If that happens to be through you... Anywhere you are in the circuit may just be a shorter path. More complications follow;

Your house ground is connected in your panel to the big block where the return, or neutral, wire is connected. This wire is a current carrier, and if you disconnect house ground, you are creating a *floating ground* in your whole house system. This makes the "ground" a part of the live current-carrying circuit, even if there are no direct problems with the circuit otherwise. This is a *potentially* very dangerous condition, especially because you don't yet know if there *is* any other problem. The potential for disaster in this case is probably fairly low in *most* houses, but in others, well, how do you know? Why play russian roulette? I would highly recommend turning the main breaker off while working to reconnect the ground. Being careful doesn't take any more time or effort than being stupid, but you'll get bitten less.

When working on the electrical system of the house there can be problems due to faulty wiring, poor design (and you would be pretty surprised to find how many houses are wired really poorly), and grounds having resistance due to corrosion, dirt, etc. Also, due to electrical wiring having resistance, and more resistance over distance, you may find even

*de-energized* circuits carrying current through you if you aren't careful (this is *usually* an example of poor design - not separating multiple circuits adequately - sharing neutrals/grounds, etc. and is very, very common in house wiring. Remember, I didn't say it was right, I said it was common). A case in point; I was recently working in a house replacing some switches and outlets. In one switch box, after de-energizing the appropriate breaker, I was pulling the white (neutral) wire out and my hand brushed up against the grounded wall box. I received a small, but quite noticeable electrical shock that made me run down to the basement to verify the right breaker was turned off and again check the circuit in the switch box with a meter. And sure enough, there was still a significant voltage present between the hot and neutral. In this case the circuit had the neutral tied into (shared) another circuit down the line, and that circuit had a light on - i.e.: the circuit was carrying current through the neutral. Due to resistance over distance (i.e.: resistance increases over distance in the wire), the distance between the open neutral I held - through me - to the grounded box, was shorter. This was of course something that we repaired. Since that time I double check every circuit I work on with a meter, and always look for inappropriate tie-ins in every box I open. BTW, while doing that, you would be surprised to find how many wire nuts aren't screwed on, and how many wires are just barely hanging on - a potential fire hazard.

[RayV]

Since this has turned into an electrical thread I'll add this:

House I bought last year has the phone, cable, fuse box, etc 'grounded' to the incoming cold water pipe. Two problems with this:

1 No jumper wire going around the meter (minor) 2 The water supply line coming through the foundation is plastic! (OK probably not *plastic* but it is not metal)

[Sailaway]

Bugs wrote

About fifteen years ago I replaced the house ground and installed a deep copper grounding rod into the ground water level at my mom's house. I ran a heavy gage wire to the panel, and disconnected the ground from the water pipe. This produced a superior ground, and probably saved the pipes, which were experiencing corrosion from electrolosis.

A few months ago, as my sisters were preparing the house for sale (mom passed on last year), they hired an electrician to do some work on the house. What do you think he did? Yup! He removed the earth ground (that was installed according to code, btw) and placed another ground back on the water pipe. Having tested the ground every year, there wasn't any problem with it, so who knows...

[Lee Michaels]

I used to do on site audio recordings. As the engineer, it was my job to make sure that all equipment was properly grounded. Audio gear that is not grounded properly develops a very loud hum (60 cycle and more) that drowns out anything that you try to record.

At least one half of the locations we recorded at did not have properly grounded plugs. I carried waterpipes in the van and drove them into the ground to get a good ground. I would connect the ground to the equipment. I also poured water on the pipes.

This, of course, got people interested. Who is this crazy guy pounding pipes into the ground? I almost got arrested a couple of times because the security guys thought I was making up this wild grounding theory. They had never heard of it.

I ended up carring around a reference book to point out the theory/science behind grounding. I also pointed out that their electrical was not up to code. And I could call it in. That usually shut them up.

[todd]

You'll have to bear with me. I'm just a stupid mechanical engineer.

So what you're saying is that there could be an existing ground fault that is currently being sent to ground through the water pipe? I take that to mean that the ground, and thus the copper pipe it's bonded to, is energized.

I'm not sure if you're referring to removing the protection permanently or long enough to put a proper clamp back on. I assumed the OP was talking about removing the ground connection just long enough to get it attached back to the pipe with a clamp. My assertion was that if there was enough voltage present in the ground wire to kill you, that you probably had other worries in addition. If that was the case, I wouldn't handle anything connected to the plumbing fixtures until the situation was corrected. Perhaps I'm wrong. Most of my work-related electrical experience was in a slightly higher range of 15-500kV when I designed insulators for distribution, sub-transmission, and transmission lines where the electrical problems encountered were somewhat different.

By the way, for the OP, one thing I haven't seen mentioned is that, at least around here, the ground is connected to the water line on just this side of the meter. Then, another ground wire bridges the meter so that the ground would still be in place in case the meter was removed.

todd