Grounding to Water Main

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Originally Posted By: dvalley
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Has anyone seen the new water mains that are entering the basements as a plastic type tubing?


When the electrical is supposed to be grounded to the water main and the main is plastic/polypropolene/some sort of tubing, what options are there to grounding the service entry to a grounding source besides a grounding rod?

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David Valley


MAB Member

Massachusetts Certified Home Inspections
http://www.masscertified.com

"Some cause happiness wherever they go; others, whenever they go."

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Originally Posted By: ismetaniuk
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This membership was a big waste of my time!

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Igor


Top To Bottom Inspections


Glen Spey, NY

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Originally Posted By: tpfleiderer
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David,


If the in coming water main is plastic then you do not have to bond to the water main within 5' of main for grounding electrode purposes (but if there are any copper or metal pipes in the house they do need to be bonded to the grounding grid of the service for safety purposes). The NEC code book ( 250.52(A) ) does give you several other options for a grounding electrode, such as the metal frame of a building, concrete-encased electrode, grounding ring or a plate electrode. But, the grounding rod is usually the most practical for a home electrical service. In our area some AHJs will make you drive two grounding rods (at least 6' apart) if you can not bound to a metal main water line 

Hope this helps

Tim

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Tim

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Originally Posted By: dvalley
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Thank you Tim… I was hoping someone would reply. Thanks again.

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David Valley


MAB Member

Massachusetts Certified Home Inspections
http://www.masscertified.com

"Some cause happiness wherever they go; others, whenever they go."

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Originally Posted By: jmyers
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David,


Tim has given some good advice. I would just like to add that the reason the metal pipes are bonded to the panel is in case they would become energized it can be sent back to the panel to trip the circuit, usually the breaker. Otherwise, the metal could be energized indefenitely and the worse case scenerio someone would touch it and get shocked.

I just wanted to clarify the reason for bonding the metal pipes so you know why it is done in that manner. Soley for safety.

Joe Myers

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Originally Posted By: tpfleiderer
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Thanks you Joe for explaining that point. Sometimes when I start rambling on, I don’t finish one thought before I go on to the next one.


Tim

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Tim

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Originally Posted By: jmyers
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Tim,


You did an excellent job of explaining the "how to" and "where to" of grounding and bonding.

I just wanted to make sure that everyone knows why the metal pipes are bonded to begin with. Taking into consideration that if you know why the metal pipes are bonded to begin with, you could reason that the plastic pipes would not need to be bonded.

BTW...Not that I am a genius or anything but you made the statement that you AHJ makes you use two ground rods in the case when bonding to the water main is not possible. Do you have any idea of the reasoning behind that? Don't the codes state they should be a minimum of 10 feet apart when a second rod is required? The second rod is only required when the impedance measurement is over 25 Ohms, correct?

What I am getting at here is, are the AHJ in your area aware of the reasoning behind bonding? Does bonding have an affect on the impedance measurement at the ground rod?

HELP me please.

Joe Myers

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Originally Posted By: tpfleiderer
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Joe,


Yes, they ask for a second ground rod when there is not a metal water pipe, because they do not carry a meggar with them on the inspection to test the impedance. So their theory is that the second ground rod will ALMOST insure them that they will have a low impedance. 

When you have a metal water pipe, that is at least 10' running in the ground, that is your first source of grounding (and almost always will have a low impedance measurement) and the grounding rod is a redundant source of grounding (as required by the code when using the metal water pipe).

BTW: The NEC listing for the ground rod distance is (250.56). They have a measurement of 6' apart when more then one ground rod is used.

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Tim

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Originally Posted By: jmyers
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Tim,


Please excuse my ignorance but I like to learn.

You are saying that since that the bonding of the water pipe does indeed lower the impedance of the grounding system, correct. That of course one would have to assume that the pipe that has been bonded is 6 feet or more away from the ground rod and as you stated that the pipe is running 10 feet or more into the earth, correct. I don't think they are not carrying them because it is too much trouble, they don't have them because they are too expensive. The clamp on models run as little as $1,000, they are not cheap. The more expensive one that I saw was running $1,500 to $1,600.

Thanks for the code clarification, I was just too lazy to pick up the book and look. If you are certain it is 6 feet I will take your word on it, I don't know where I picked up the 10 feet.

Joe Myers

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Originally Posted By: tpfleiderer
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Joe,


When you use a metal water pipe as your first grounding electrode, the AHJs, around here, believe they are covered (for not testing the impedance to ground) by the code, because when you use a water pipe as your grounding electrode the code states that you must supplement that electrode with another type of electrode. SO, when you use the metal water pipe as your electrode you will always have two grounding electrodes, which means that you have a much better chance of being below 25 ohms to ground.

The requirement to supplement the metal water pipe, when used as a grounding electrode, is based on the practice of using a plastic pipe for replacement when the original metal water pipe fails. This type of replacement leaves the system without a grounding electrode unless a supplementary electrode is provided.

Which brings back to the original question "What other options do you have when plastic is used for the water pipe?" See after all of this we really were staying on topic!

Hope this has helped with which ever part of my statement before was confusing.

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Tim

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Originally Posted By: roconnor
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Tim … good job explaining the basic service grounding requirements. The rule I always followed for a new house is two (2) grounding points for a service ground, unless testing is performed.


For a new house the code allows a service ground to a metal water service pipe with at least 10 of length in the earth, but there also must be a supplemental ground rod (2 ground points). This supplemental ground rod is not required to meet the 25 ohm resistance the way I read the code, unless you take a very restrictive position (a little much in my opinion).

Also, I have heard that some water companies now require an isolation coupling between the house and the street connection to help avoid shock hazards for water company workers, so you have to be aware when a house is very close to the street (or an existing ground is to an abandoned service pipe) that the pipe is embedded at least 10 feet into the ground.

For plastic water service pipes, or pipes embedded less than 10 feet, the service ground can be just a single ground rod with a resistance of less than 25 ohms. But, this requires testing (I am also a p/t AHJ, and the contractor is required to perform the testing to prove the 25 ohm resistance ... the AHJ isn't responsible for testing).

The code provides for the installation of a second ground rod where this resistance is not achieved (2 ground points). Again, where two ground points are provided testing is not required. It is usually easier for a contractor to just install the two ground rods to avoid the resistance testing.

There are other options when you have a plastic water service pipe, like a ground ring around the house or concrete encased electrode within or near the footing at least 20 feet long, although these options are not as common.

Older homes may only have one ground point to the metal water service pipe, as the supplemental ground rod is somewhat a newer requirement. In my opinion this is acceptable for an existing home as long as it is not an abandoned service and it?s a tight connection before the water meter within 5 feet of the house entrance. On some houses the ground clamp is loose or may have been re-attached to a section of pipe that wasn't? cleaned, which needs to be corrected.

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Originally Posted By: tpfleiderer
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Welcome to the board Eagle,


This does show how the requirements and the NEC interpretations of the AJHs do vary from place to place.

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Tim

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Originally Posted By: roconnor
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Thanks for the welcome Tim. This seems like a good place to discuss home construction and inspection issues.


You are correct that AHJ's interpret the code differently. Some joke that the code is not what is written in the book, it is what the AHJ says the book requires ? some truth to that. On this issue I think some AHJ's do not really read the current code requirements correctly.

If a supplemental ground rod needs to be tested for the 25 ohm requirement (or a second supplemental rod installed), then there is no need for the water service ground as the supplemental ground rod(s) would qualify as a primary grounding point. See where I am going with this.

I think the intent and wording of the code is simply that for a new home there has to be two (2) acceptable ground points, or testing is required.

[As in the International Residential Code (IRC) section E3805, and 2002 NEC also. IRC Section E3805.1.1 only requires one (1) ground rod to supplement a water service ground, and does not require it to be tested].

In my opinion the supplemental ground rod provision is intended to provide redundancy in the event the water service ground is temporarily removed to work on the pipe. It also provides minimal protection where a metal water service pipe is abandoned or replaced with plastic. Even though the code would require that the former ground be replaced (2 ground points) or that the supplemental ground rod then be tested to qualify that as a primary ground point.

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Originally Posted By: tpfleiderer
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Eagle,


As stated in the NEC 2002 handbook, The requirement to supplement the metal water pipe, when used as a grounding electrode, is based on the practice of using a plastic pipe for replacement when the original metal water pipe fails. This type of replacement leaves the system without a grounding electrode unless a supplementary electrode is provided.

So, I would say that the supplementary electrode would (or should) meet the less then 25 ohms requirement. As we both know when that water pipe gets changed from metal to plastic the last thing that the plumber is going to think is "we need to get the resistance of that supplementary electrode checked". 

Having said that, as I stated above, when I was a AJH, I did not have the megger to do the testing, nether did the contractors that I inspected for. So none of the electrodes got tested

This is just my thoughts

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Tim

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Originally Posted By: roconnor
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Tim … as an AHJ I don?t think it’s a big deal if contractors don’t test the ground rods (even though I would recommend it), and long as a single ground rod is just a supplementary ground, or two ground rods are installed if that is the primary ground point.


I also think that a code requirement for a supplemental ground to be tested for the 25 ohm limit, or to require two supplemental grounds, in addition to the water service ground, doesn't make sense. It is then a primary ground point and the water service ground wouldn't be required. The IRC is pretty clear on this ? haven?t checked the actual wording in the 2002 NEC lately since IRC is a ?stand-alone? code.

I understand your point about upgrading to a plastic water service pipe, but the codes are only suppose to be minimum standards to ensure a reasonably safe installation that is economical. They are not intended to anticipate a future code violation. I think having the primary water service ground and one untested supplementary ground rod is reasonable from a minimum code standpoint. The conversion to a plastic water service pipe, and potential code violation, is something a home inspector needs to be aware of ? like other potential code violations. If every modification was done to code, there wouldn?t be as much a need for home inspectors.

That isn't to say that a builder/designer/homeowner wouldn't want to make sure that the supplementary ground can also meet the primary grounding requirements, for extra safety and to avoid the potential expense of testing or the cost of installing an additional ground rod in the event a water service is replaced with plastic pipe.

Just my two cents (or nickels if you consider inflation ... lol)

Rob

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Originally Posted By: dvalley
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Tim and Eagle,


Thank you so much for the info on grounding the service to the water main. I was never aware that when a plastic main entry is seen,
that the water pipes were serviced and changed. I know exactly what to expect when checking on the grounding source now.
Most homes that I inspect don't have the secondary grounding wire installed across the meter. So I point that out to my client.

What year was this second ground wire (across the meter) demanded?


Thanks everyone.

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David Valley
MAB Member

Massachusetts Certified Home Inspections
http://www.masscertified.com

"Some cause happiness wherever they go; others, whenever they go."

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Originally Posted By: roconnor
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Dave … If you see a plastic water service pipe it doesn’t mean it was necessarily a replacement. For a newer home it could have been built that way, although that is not very common in my area. But a replacement is usually pretty obvious.


For new home construction I look for two (2) acceptable service ground points, or ask to see the test results if it's a single ground rod.

For an existing home service, I look for at least one good ground. This is usually a ground to a metal water service pipe, and it's important that it be a tight connection before the meter within 5 feet of the entrance.

If you see a single ground to an abandoned water pipe, or an obvious upgrade to plastic pipe without a supplementary ground, it's a red flag.

If you only see the water service ground in a newer home, or an upgrade to plastic pipe in a newer home and you can?t verify two ground points/rods, to me it's something to be noted, and I would probably recommend an electrician verify adequate service grounding. Although, some say that only one good ground to a metal water service pipe even in a newer existing home is accetable.

Tim ? what would be your take on this? 

Rob

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Originally Posted By: tpfleiderer
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Dave,


Not sure which year that bonding the water pipes was put into the code book. Rob is correct on the plastic pipe, they are now using that for new installations as well as repairs. it is easier and cheaper to install then metal pipe.

BTW: I would like to point out, that the reason for having the wire across the water meter is not for grounding grid reasons, but for bonding reasons (see Joe M's explanation above on bonding). The reason for this wire is so that if the water meter is taken out you will not loose the bonding of the metal water pipes. When I was a AHJ we also required a bonding wire installed across the inlet and outlet pipes of the water heater for the same reasons. 

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Tim

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Originally Posted By: mpetner
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The use of plastic service pipe, atleast in some municipalites, is subject to the rules set forth by the local Licenses and Inspections Department, regardless of whether or not it?s new construction. Even for new construction, copper may still be required. Polyethylene services, aside from the ease of installation and cheaper cost, may be required in order to isolate the water main in the street for corrosion control purposes. Stray currents, as well as corrosive soils, can significantly corrode ductile iron and cast iron water mains in the public right-of-way. In some municipalities, usually larger cities with alot of underground infrastructure, plastic pipe may be require for corrosion control purpose. It?s all based on engineering studies. But in some cases, copper may still be required for some municipalities, unless conditions require the use of plastic pipe.

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Originally Posted By: roconnor
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Tim … good point about the difference between the grounding system and bonding. Where bonding is just a connection of metal parts that could become energized (service panel, all above grade metal piping, etc.) to the grounding system. This is important to prevent shock hazards.


I also noticed that the bond between the hot and cold pipes at a water heater is frequently missed (water heater could isolate the bonded cold water inlet pipe from the hot water outlet pipe, and thus could become energized).

BTW ... metal gas piping above grade in a house must be bonded, but this is NOT permitted as a grounding point by code. 

Rob

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