ECN Forum Forums General Topics of the Trade General Discussion Area Grounding to water pipes

I think now that my quote from the utility was probably just badly written and did not mean what it seems to say. They probably meant "..used for grounding" or something to mean that it was being made part of the grounding electrode system.


Bill

[QUOTE]Originally posted by Dspark:
>[b]My brain is too tired to imagine the difference
Simply put, it is bonded, but it cannot be counted as a required electrode.

Dspark,
What I'm wondering is the ramifications of possible current flowing on the gas line that is bonded as opposed to if it is used as an grounding electrode. Bonding it makes it part of the grounding electrode system. So, if the reason it is not allowed to be an electrode is to minimize the likelihood of current flowing on it, so gas workers don't get zapped, doesn't bonding it defeat this.


[This message has been edited by Redsy (edited 07-26-2001).]

Redsy,

If there are insulating bushings then it's a non-issue, right?

Bill

Bill is right that is the gas company, water company, or whoever is worried about this, they can place a dielectric coupling in the line.

>Bonding it makes it part of the grounding electrode system.
Depends on whether the insulating bushing is there. I'm just saying that it can't count as 10' of buried metallic pipe for an electrode.

>doesn't bonding it defeat this.
The gas man can and should use effective means of electrical jumpering before he breaks continuity. The unsuspecting house dweller can't test the gas lines for voltage before touching them.

I think the risk to the gas man is greater if the gas line is not bonded. If it is bonded, it won't have a full 120 V on it. If it isn't bonded, it just might be energized at a full 120 V.

If a child walks up to a gas meter and touches it, she shouldn't get electrocuted. My job is to try to prevent that no matter what the gas company thinks.

I beg to differ with you Dspark. I have been on many trouble calls where someone is getting shocked from the kitchen sink even to the shower. In all cases the culprit was a bad neutral connection. Alot of folks notice the lights dim/bright(bad neutral) but fail to call the utility to check it out. Most times on these calls I will ask the customer how long has it been doing this? 85% of the time they will tell me that it has been like that for a couple of weeks. Yea weeks!! That tells me that it started way before 2 weeks ago in order for the ground rod to bake out and be of no more use. Then that is when the shocks come into play. I have found voltage line to neutral at full line to line voltage!! 240 big ones . Mind you that is extreme cases. But just think for a moment,
N-L1=0 v
N-L2=240 v
L1-L2=240 v

That neutral is looking for a path back to its source(transformer). If you just so happen to provide that path then you are in for a big surprise. The pipes in the house will be energized, but more than that they will be carrying the full neutral load of the service!! Voltage does not kill but amperage does. Getting into "series" with a neutral that has a load on it will kill you quicker than if you stick your hand into a hot buss.

If it were a perfect world there would be no need for grounds at all but it is less than perfect. So I do agree that the plumbing should be bonded so that they are at or near earth potential. But to say that something cannot happen, well it does and will continue. Probably not to the point of death but.......

Just remember that a neutral is "THE" most dangerous conductor there is in the electrical field.

I said, "That is not possible if everything metallic is properly bonded.".

Glenn replied, "I have been on many trouble calls where someone is getting shocked from the kitchen sink even to the shower."

Could you please suggest for me a path that the current may have followed and why proper bonding did not prevent this (even when the neutral was disconnected); or more to the point, how bonding created a shock hazard that wouldn't have existed had the water pipes and gas lines not been bonded?

I would think that if any current is flowing on the piping system and it encounters a poorly conductive joint, as might be the case across some pipe dope or plumbers putty, a potential difference will exist and present a shock hazard of some degree. I guess it all depends where the bonding occurs in relation to the fault. If the person touches the higher potential side of a poor pipe joint and the other (low potential) side where the bonding to a gas line occurs you will have a possible safety problem.
Anyone?

I don't believe that pipe dope prevents metal to metal contact.


In any event, the described fault was a broken neutral between the point of service and the transformer.

>If the person touches the higher potential side of a poor pipe joint and the other (low potential) side where the bonding to a gas line occurs you will have a possible safety problem.

The could be said if the person touched a water line, drain, vent, or structural steel. Shall we also not bond any of those?

I specified that everything had to be properly bonded, and that including the gas line in the bonding would not create a new hazard even if the neutral broke.

I would never try to suggest that any installation is safe unless everything is either bonded or insulated.

So of course as soon as you start with the premise that something isn't properly bonded, I will immediately concede that a hazard exists.

If everything else is properly bonded, then bonding the gas line also cannot create a new hazard that wouldn't exist if the gas line were not bonded...
even if the neutral is disconnected.


By the way, I saw an installation where the a panel of a duplex residence was grounded just to the bath tub in the adjoining unit. At one time there was a copper line between the units and one unit was grounded to that line. By and by, a water softener was installed and most of the water pipes were replaced with plastic. The only remaining copper ran to the upstairs bath room. No one ever complained of a problem with that and I would guess that it was that way for at least 10 years judging by the age of the softener.

Current has to be able to follow a path. There was nowhere to go from the bath tub.

This has been another true story backing up my belief that waterlines shouldn't count as required grounding electrodes.


[This message has been edited by Dspark (edited 07-27-2001).]

Dspark qoutes"Could you please suggest for me a path that the current may have followed and why proper bonding did not prevent this (even when the neutral was disconnected); or more to the point, how bonding created a shock hazard that wouldn't have existed had the water pipes and gas lines not been bonded?"

As we all know, electric current will follow any given path to ground.

Differences in potential is the key word here I beleive.
If the water line is metal on the inside of the house, PVC going into the ground then it is "isolated" from ground. Bond the water line to the electrical system and now it is bonded. With a baked out or non existent ground rod and a broken/disconnected neutral you have isolated your water line once again from grnd. Although it is isolated from grnd it is also isolated from the source. The path would be someone that touches the water line or its connected fixtures and is touching a ground. Dspark you used the example of an upstairs bath. I'll give you that one because the person himself would more or less be as a bird on a wire. But what if that person was downstairs on a concrete floor, barefooted, and touches that line? Or if that person is standing outside barefooted and reaches for the spicket(which is bonded)? There are many instances that a person can be grounded. The scenario I am using has made the waterline just as energized as any ungrounded conductor!

As I said before I do agree that it should be bonded. But bonded or unbonded a hazard could exist either way. Which would be the most likely to occur? I haven't a clue. It is one of those things that you are damned if you do and damned if you don't.

One last question for all you sparkys out there.
When you arrive on a job and you open the breaker box how do you go about it?

Do you just reach and grab and open it up?
Or do you sweep the back of your hand across it?

My dic* has been knocked in the dirt a couple times when I just reached and grabbed.
What made that box hot? Ahhh, a bad neutral conn. and a non existent grd rod or a baked out grd rod!

[QUOTE]Originally posted by Dspark:
[B]I don't believe that pipe dope prevents metal to metal contact.


I am not suggesting it prevents metal to metal contact. Only that it will introduce a certain amount of impedance. And possibly a voltage drop.