plastic water systems

[Joseph Alexander]

My issue is with water systems that are entirely made of plastic (not only the lines within the house but the main service line as well). It seems to me that bonding this water system to the electric system or using it as a ground becomes an issue. Basically you can not do it. It wouldn?t do any good even if it were done. According to the NEC the first choice of a grounding electrode is the cold water pipe. (250.52(A) (1) But, only if the ?metal? underground water pipe is in direct contact with the earth for at least 10' (3.0 meters) and then this connection must be made within 5' (1.52m) of the point of entrance of the water pipe. If as mentioned above the water line entering the home is plastic then the water system cannot be used as part of the ground electrode system. If the main is plastic and the remainder of the system is copper, or other metal, then the water system must be bonded to the electrical system. However the issue here is when the entire water system is plastic (or some other non conductive material) then grounding and bonding becomes (as far as the code books are concerned) unanswered questions.

1. Will GFCIs in the bathrooms or kitchen even work? If the main municipal water line is plastic as well as the components with in the home then there is no path to ground and thus no return path to the electric system. Even if you consider the water within the pipes (which is at best a poor conductor) the resistance should be so high as to allow little or no current flow which would trip a GFCI
2. Does the hot water heater need to be grounded. Here I would think not because there is a ground provided with the service wire (NM or MC) which effectively grounds and bonds the device.
3. What if the gas line is also plastic? Do you need to bond the heater? Again the wire feeding the heater should have a ground with it providing the necessary ground/bond?

I realize that seems like I have answered my own questions. But what I am looking for is how is this being dealt with in the real world. Since this should be a fairly new issue as a good deal of the new houses being built are being plumbed with all plastic pipes. I would really appreciate some feed back. Most of this seems cut and dried, but you never know what the AHJs are going to decide to do with this issue!

 

[edamico11]

Joseph

Joseph

check question about your post....

Of course you cannot use the plastic piping system, but then just find two other alternatives.,,, ground rod's, etc. are you just upset that it forces you to go another route..??

ed

 

[don_resqcapt19]

1. Will GFCIs in the bathrooms or kitchen even work? If the main municipal water line is plastic as well as the components with in the home then there is no path to ground and thus no return path to the electric system. Even if you consider the water within the pipes (which is at best a poor conductor) the resistance should be so high as to allow little or no current flow which would trip a GFCI

Don
If there is no return path, then there is no current flow and no hazard. If the path can flow ~5mA the GFCI will trip if the is a ground fault.

 

[charlie b]

There really are no ?unanswered questions,? as you put it. This is an easy situation to deal with.

First of all, planet Earth has very little to do with how a home?s electrical system operates. There are good reasons to have a good Grounding Electrode System (i.e., ground rods, connection to metal water pipes, UFER grounds, etc.). But the reasons do not include creating an effective path for ground fault current to return to the source. That path is created by the ground wire that is run with the other conductors.

Secondly, a GFCI receptacle does not require a ground (specifically meaning an Equipment Grounding Conductor) to be able to operate. It compares current on the phase (i.e., ?Hot,? or ?ungrounded?) conductor with the current on the neutral (i.e., ?cold,? or ?grounded?) conductor. If they differ by more than 3-5 milliamps, it will trip.

Finally, 250.50 says to look at the list of possible grounding electrodes, as shown in 250.52(A)(1) through (A)(6). Then it tells us that any that are present must be used. OK, so in your situation the water pipe is not present. No problem. All you have to do is (1) Don?t use it, and (2) Look for the other five, and use any that are present.

 

[mark henderson]

Finally, 250.50 says to look at the list of possible grounding electrodes, as shown in 250.52(A)(1) through (A)(6). Then it tells us that any that are present must be used. OK, so in your situation the water pipe is not present. No problem. All you have to do is (1) Don’t use it, and (2) Look for the other five, and use any that are present. [/SIZE]

Nice anwser I has flipping through the code and got that info and then saw that you are quick to the draw

Mark:smile:

 

[raider1]

First off we need to have a grounding electrode system installed in accordance with 250.50. If the water service pipe is plastic then it can't be used as a grounding electrode. You do still need to use another grounding electrode of the other types listed in 250.52. This grounding electrode system WILL NOT help in tripping a breaker or blowing a fuse. Here is what the NEC states the purpose of the grounding electrode system is:

Electrical System Grounding. Electrical systems that are grounded shall be connected to earth in a manner that will limit the voltage imposed by lightning, line surges, or unintentional contact with higher-voltage lines and that will stabilize the voltage to earth during normal operation.

This quote comes from 250.4(A)(1) of the 2005 NEC.

Second, if we don't have a "metal piping system" then there is nothing to bond to in accordance with 250.104(A).

In answer to you first question "Will GFCIs in the bathrooms or kitchen even work?"

Yes, a GFCI doesn't rely on the grounding electrode system to work.

"Does the hot water heater need to be grounded. Here I would think not because there is a ground provided with the service wire (NM or MC) which effectively grounds and bonds the device."

Correct, if you have an electric water heater it must be grounded and bonded, but the equipment grounding conductor run with the circuit that feeds the water will ground and bond it.

Chris

 

[Pierre C Belarge]

The water pipe is required to be supplemented if it is used. If the water pipe does not exist, one does not need to have more than one electrode for the electrode system, if only one electrode is present/made.
Lets say the water pipe electrode does not exist, and there is only the steel electrode. Only the steel electrode would be required, so no rods or other "supplemental" electrode is necessary.
The same could be said for the "other" electrodes.

The code does not say that water has to be used for the electrode if it is present/available. One could use the steel as the electrode, then bond the water to the grounding electrode system. 250.50 & 250.64(F)

 

[coulter]

...There are good reasons to have a good Grounding Electrode System (i.e., ground rods, connection to metal water pipes, UFER grounds, etc.). ...

Reasons (plural) - Humm, I can think of only one. So what are a couple - two anyway? - unless you are going to use, "The code says so." In which case, three would be nice.

carl

 

[Pierre C Belarge]

Stablize the voltage
Earth refence

 

[charlie b]

Stablize the voltage

Earth refence

It might be said that those two are very similar, if not actually the very same reason. The other reason I can think of is to prevent a lighting strike from creating a sustained elevated voltage on a structure (i.e., to give the lightning an attractive path to its home planet).

 

[coulter]

Stablize the voltage...

How does it do that?

...
Earth refence

So why would that matter?

I'm serious. I can't tell that grounding promotes safety at all. The only thing I can think of that is difficult to protect against on ungrounded systems is restriking, arcing faults.

PS: I'm not stuck and can be educated.

carl

edited to fix the poor syntax

 

[don_resqcapt19]

Pierre,

The code does not say that water has to be used for the electrode if it is present/available

It doesn't?
Don

 

[charlie b]

Well, you don't have to use water. But you do have to use the water pipe, if it's available. :wink:

 

[charlie b]

I can't tell that grounding promotes safety at all. PS: I'm not stuck and can be educated.

Good question. Unfortunately, I don?t think I can give a short answer. So bear with me, if you will.

Voltage is the difference in ?potential? between two points. ?Potential? can only exist in the presence of an electric field. Depending on the orientation of the field (i.e., which way is Plus and which way is Minus), and depending on the nature of a packet of charge (i.e., again, whether it is plus or minus), the field will either help push the charge or it will fight you as you attempt to move the charge.

?Potential? is a bit of an obscure concept. But you can look at it like this.

Suppose we live in separate houses on the same road. It is a very, very long road. There is a town somewhere way, way beyond your house. I am not going to tell you the name of the town, nor how far that town is from your house. Suppose that if a car started at that town and drove to your house, it would take 70 gallons of gas for the trip. Suppose that if the same car driving the same way under the same conditions drove from that town to my house, it would take 90 gallons of gas to make the trip. Can you tell me how much gas it would take for that car to go from your house to my house? Did you need to know the location of that town, in order to arrive at your answer?

Now suppose there is an electric field in the vicinity of our two houses. Suppose someone wants to move a packet of charge (let?s say it is one coulomb of charge) from ?that town way, way over there? (the usual engineering term for this is ?from infinity?) to your house. It will take some amount of energy to make that trip. Let?s say it took 70 joules of energy. Suppose instead they moved the same amount of charge from ?that town way, way over there? to my house, and it took 90 joules of energy to make the trip. What is the voltage between your house and mine? It is a difference in potential of 20 joules for every coulomb of charge you try to move from your house to mine. A ?Volt? is defined as ?one joule per coulomb.? Thus, the voltage between your house and mine would be twenty volts.

Now to your question. Start with an ungrounded system (i.e., no ground rods). If there are 120 volts between the hot conductor and the neutral conductor, then what is the voltage between the hot conductor and planet Earth? How about between the neutral conductor and planet Earth? This is similar to asking the distance from "that town" to your house or to my house. The answer is that you don?t know. And as far as the light bulb, the TV set, and the coffee pot are concerned, it does not matter. You could have a voltage of 1,120 volts from the hot to ground, and a voltage of 1000 volts from the neutral to ground, and the difference is still 120 volts, and the coffee pot will work properly.

So why is this a problem? Because the internal wiring of the coffee pot is designed to stop current from leaking from the energized parts to the outside world, provided that the voltage between the energized parts and the planet is not over 600 volts (the standard insulation rating for most of what we deal with). But in my example, the voltage is almost double the insulation?s rating. That would not be safe.

How do we stop that from happening? By connecting the neutral wire (at the main service) to planet Earth. That causes the voltage at the neutral and the voltage at the dirt to be almost the exact same value. That in turn causes the voltage between the hot conductor and planet Earth to be no more than about 120 volts. There may be some variation from moment to moment. But the voltage rating of the insulation systems of all household electrical appliances will not be exceeded.

 

[Pierre C Belarge]

Pierre,

It doesn't?
Don

I was waiting for a response to that statement...

250.50 requires a "grounding electrode system".
For instance:
I use the steel of a structure as the electrode my grounding electrode conductor (GEC) is terminated to. (The steel is "effectively grounded")
I then only have to bond the other electrodes to the electrode/GEC from the steel.

In this example, the water pipe would be bonded to the steel to help create my Grounding Electrode System.

What I probably should have said is the water pipe electrode does not have to be directly connected (with a GEC) back to the service disconnecting means enclosure.

 

[LarryFine]

The water pipe is required to be supplemented if it is used. If the water pipe does not exist, one does not need to have more than one electrode for the electrode system, if only one electrode is present/made.

So, if we're using the water pipe as an electrode, we must have two rods, but if we're not using the water pipe as an electrode, we only need one rod? We can eliminate the second rod by keeping the pipe clamp more than 5' from the entrance of the pipe?

 

[charlie b]

So, if we're using the water pipe as an electrode, we must have two rods, but if we're not using the water pipe as an electrode, we only need one rod?

No, you still need two (or you need the first to have a resistance of 25 ohms or less). 250.53(D)(2) sends you to 250.56. But 250.56 stands by itself, no matter what other section sent you there.

We can eliminate the second rod by keeping the pipe clamp more than 5' from the entrance of the pipe?

No, if the water pipe is available as an electrode (i.e., in contact with dirt for 10 feet and is accessible within 5 feet of the entrance), then it must be used as an electrode.

 

[coulter]

Charlie -

Excellent disertation. As for terms, potential, tension, voltage, and probably a few others, all work.

....How do we stop that from happening? By connecting the neutral wire (at the main service) to planet Earth.

Yeah, that would work. Of course, the house neutral is now elevated to the same potential as the distribution neutral - could be several volts above earth. A surge suppressor may work as well and not have the displacement. I suspose the connection that bothers me the most is the one between the distribution neutral/ground and the house transformer neutral.

....How do we stop that from happening? By connecting the neutral wire (at the main service) to planet Earth. That causes the voltage at the neutral and the voltage at the dirt to be almost the exact same value....

I don't know about that -- maybe if you stay within 1" of the ground rod. I'd say three feet out, if there is 120 on the ground rod, then the the tension between the earth and the rod is 120V.

I think we get stuck by "US is best - or in this case, North America is best". And being the patriot I am, I tend to agree. However, there are some other countries that use different grounding schemes that work pretty good.

carl

 

[LarryFine]

No, if the water pipe is available as an electrode (i.e., in contact with dirt for 10 feet and is accessible within 5 feet of the entrance), then it must be used as an electrode.

Okay, glad you mentioned that. I have had inspectors tell me that, unless I am willing to unearth the incoming water supply, I cannot prove that an existing metal water pipe is unbroken for that first 10 feet underground.

By the same token, if they are unable to prove to me that the unbroken 10 feet does exist, how can they require an existing pipe to be used as an electrode? In other words, that I connect within the required 5 feet of entrance.