To remove dangerous voltage on metal parts from a ground fault,
electrically conductive metal water piping systems, metal sprinkler
piping, metal gas piping, and other metal piping systems, as well as
exposed structural steel members """""""that are likely to become
energized"""""""", must be bonded to an effective ground-fault current
path [250.4(A)(4)]. Although bonding isn’t required for isolated
sections of metal water piping connected to a nonmetallic water piping
system, metal water piping systems must be bonded in accordance with
My house is about 40 years old. I just took a hit on my computer
equipment. I think it is because the CATV is bonded to my cold water
pipe. I don't think the copper pipe is grounded.
My water heater is gas so it is unlikely to become energized. Is the
copper pipe in my basement required to be grounded?
Can I make the CATV guys ground their equipment to my service mast as
my grounding electrode is likely buried on an inside wall that is
covered with sheet rock and a concrete floor?
Your internal copper water pipe, except small isolated sections, should be
bonded to the grounding electrode system, which in your case is going to be
one or two driven ground rods connected to the neutral/ground bar of your
main service panel.
The CATV guys will ground their equipment to anything they can find that's
The thing I am pondering now it that I have a dead modem, dead router,
and 2 dead motherboards.
I would like to be able to pin it on the CATV guys as it almost had to
come in on the CATV as I have a UPS and both computer power supplies
are good. The only thing that was not connected to the surge
suppressor were the Cat 5s going to the network cards. That was an
over site on my part as the UPS does have network jacks.
I agree with you that the piping "should" be grounded. I want to know
if it "has" to be grounded.
I think it was you that posted a link to the NEC online once. Do you
still have that link? I saved the link, but the computer is not
working at the moment. :)
As always, thanks for you suggestions.
On Thu, 26 Jul 2007 19:43:16 -0400, "RBM" <rbm2(remove
Originally your water pipe was required to be used as a grounding
electrode and connected to the power system ground. That connection now
has to be within 5' of the entrance of the water pipe to the house. Your
house is old enough the connection could have been anywhere.
With the PVC water service you now have, the interior metal water pipe
has to be bonded to the electrical system ground with similar rules, but
the connection no longer has to be within 5' of the entrance. Bonding
requirements are in 250.104-A.
If the water pipe is not connected to the power system ground it is not
the CATV guy’s problem.
The requirements for grounding electrode for CATV are in 820.100-B.
(They are about the same for phone.)
The only point on water pipe that can be used for the CATV ground is the
first 5 feet inside the house. (This may have been different in the past.)
Your metal electric service mast is another permissible grounding point.
(In recent versions of the code, there has to be an accessible point
provided to connect the CATV, phone, ... ground to.)
The grounding conductor from the CATV entry block has to be 20' or less,
(or a ground rod has to be added and the CATV block still has to connect
to the power grounding system). But the connection from the CATV entry
block to the earthing wire at the power service should be as short as
possible as I said under single point ground in your previous thread.
You don’t describe your computer setup. If you have widely separated
computers, each connected to its own suppressor, and interconnected by
ethernet, a surge can shift the ground potential at one end resulting in
a high voltage between computer and ethernet cable at both ends.
As I said in your previous thread, when using a plug-in suppressor all
interconnected equipment needs to be connected to the same plug-in
suppressor, or interconnecting wires need to go through the suppressor.
And external connections, like ethernet, phone, CATV also need to go
through the suppressor . Connecting all wiring through the suppressor
prevents damaging voltages between power and signal wires. A UPS can act
as a plug-in suppressor.
If *all* equipment was connected to the same suppressor, the ethernet
cables wouldn’t have to go through the UPS.
Another question is what are the surge protection ratings of the
Originally my house was supplied by a well. The house has a partial
basement and a crawl space. The well is located in the crawl space.
The first drop from the well is to the clothes washer. (This could
actually be the grounded part if the pipes are indeed grounded. The
panel is located on an inside wall in the washer/dryer room. That
part has a poured slab floor) My health is not good, so crawling
under the house is a big deal. I did take a flashlight and look. None
of the copper pipe is even in contact with the earth although I would
not have been able to see a ground clamp if there was one.
Would it not be the CATV guy's problem if the pipes were PVC? Everyone
now a days uses PCV for repairs. I pay $100 a month for
Internet/Cable. I think I would be justified in asking them to come
back out and ground their system to the service mast. I am still
considering asking them to pay for my computer repairs.
other. There were actually 3 all plugged into the same place. The
cheapest one that I had built from spare parts didn't get damaged.
All 3 computers were plugged into the same UPS (1500va). The router,
modem, speakers and monitor were also plugged into the UPS. One of
the computers that took a hit was plugged into the surge suppressor
only jack (No battery backup) The other one that took a hit was on
battery. (I only have one monitor. I use a KVM switch)
The thing that is most puzzling to me is what was damaged. Changing
the modem fixed my Internet connectively problem. I also have a
wireless laptop. The laptop could still talk to the good computer,
but neither computer could access the Internet. Changing router
allowed them to talk to the Internet.
This causes a question. Why would the LAN card still be good in one
computer and take out two others plugged into the same router? For
this to happen, the hit would have to enter in the cable modem. It
then would have had to continue on the CAT 5 cable. Then through the
router to fry 2 out of 3 motherboards.
The power supplies in all 3 computers are good.
All the equipment was connected to the same suppressor.
If I were the cable company, and if you had interior metal water pipes,
I would argue that the NEC (if it is enforced in your area) requires the
water pipe to be either bonded (pvc water service) or connected as a
grounding electrode (10' underground metal water service). In either
case I (the cable company) would argue that I connected the cable to a
permissible electrode (assuming they did) and that it was not my
responsibility to verify that all water pipes are connected to the
electric service properly. Of course you could try asking them to pay.
If the CATV drop is near the power service, I suspect they would move
the grounding point to the metal service mast.
Sounds like a good possibility. I don't remember you wrote the CATV lead
went through the UPS/suppressor.
Particularly if there is *no* bonding between CATV entry and power
service to shunt some of the surge, that could result in a surge too
large for the suppressor (which may now be damaged).
For damage you need a difference in the voltage between power and CATV.
Particularly with no interbonding that could also result from a surge on
the power lines. And if the electric service is not earthed at the house
the possibilities grow.
And low suppressor ratings could be a problem.
First you should ensure that your electrical system is properly grounded,
otherwise moving the cable ground connection to the mast or any other part
that should be grounded but may not be grounded, could provide no protection
at all. After all your copper water pipe should have been grounded but
wasn't. All metal parts of the building operating system should be grounded,
it is your job to ensure that they are grounded by what is considered an
acceptable ground according to your local electrical code and/or the NEC.
For this reason I don't think you will have much success with a claim
against the cable company.
Well this is still my question. What if some of the piping gets
replaced with PVC? It happens all the time. I see no reason to have
to rely on the copper in the basement as a grounding path. The CATV
should be bonded to the service mast.
Thanks for you time.
That is why the US NEC forbids piping that is further than five feet
away from were the piping comes out of the earth being used as a
Grounding Electrode. If the cable installer connected to the water
piping at any greater distance then the installation was in violation of
the National Electric Code.
A point about code changes in the past 40 years: pipes installed by
a plumber should not achieve electrical code grounding requirements.
Electrical code wants its own earthing and wants its own dedicated
bonding. Meanwhile, electrical code still demands that piping be
bonded - so that pipes do not become energized and become human safety
problems. That electrical source could be either inside the house or
via city pipes. Either way, that electrical danger is made irrelevant
when bonded to AC electrical box ground. All this grounding defined
only for human safety.
Your question is not about human safety. Your question is about
transistor safety. That means earthing must exceed what code
requires. For example, if cable was 'grounded' by a water pipe, well,
was it earthed? Even that pipe length can mean grounding but not
earthing. Sharp bends and solder joints are more reason why lightning
will also take other, destructive, paths into the house.
That is your problem. Lighting surge was permitted inside the house
where protection inside numerous appliances was then overwhelmed.
How could NICs and router be damaged? A similar example. Lightning
struck AC electric. Surge protectors adjacent to two computers simply
connected that surge from black 'hot' wire to many other wires into
each powered off computer. Surge was shunted from black wire to green
wire and through network card on two computers. Surge traveled via
network into a third computer's NIC card. Through motherboard ground,
out modem, and to earth via phone line. Semiconductors in network
cards and modem replaced to restore entire system AND to trace that
Surge entered via the most common entry wire - AC electric. Surge
found a path to earth ground via phone line. Phone line appliance was
damaged by a surge that entered on AC electric. Surge was shunted
into two powered off computers to find earth ground, destructively via
a third. Surge that was not earthed before entering a building will
find too many destructive paths. Fix one, and the surge will find
another. Solution is always to earth that surge before it enters a
A surge need only overwhelm protection in one location to then
become a good conductor to earth. One damaged computer may simply act
as a surge protector; destructively protecting other electronics.
That destroyed component made a better path to earth so that a surge
did not overwhelm protection inside other components.
Once a surge is permitted inside the building, then solutions become
too complex. Fix one potential surge problem, and the next surge will
find another destructive path through another appliance. A surge must
be earthed before it can even enter the building so that protection
inside all electronics is not overwhelmed.
Water pipes are typically bad grounds for transistor safety. Pipes
are too long, too many 90 degree bends, solder joints, etc. Most
important - each incoming wire must make a dedicated connection of
'less than 10 feet' to the same earthing electrode. How those
connections are installed is as critical as electrode resistance -
short, no bends, no splices, separated from all other non-earthing
wires, all earthing wires are independent until all meet at the
earthing electrode, etc. A summary was posted in comp.sys.mac.comm on
4 Jul 2007 entitled "DSL speed" at
Pipes are traditionally poor earthing connections. This made worse
when the incoming pipe is not within a 'less than 10 foot' connection
of breaker box and telco provided surge protector. Discussed is the
difference between grounding for human safety verse earthing for
transistor safety. Protection means a surge must be earthed before it
can enter a building. CATV must make a short connection to same
electrode that all other utilities also make that short connection to.
Grounding to pipes (not to be confused with bonding) is not acceptable
as it was 40 years ago.
Meanwhlle above only defines secondary protection. Your modem,
network, etc protection also means the prmary protection system must
Surge danger means that all incoming utilities must be earthed to
the same electrode. Just another reasons why all utilities should
enter the building at a common point - the service entrance. Each
utility makes a 'less than 10 foot' connection (beyond what code calls
for) for surge protection.
Meanwhile code also recommends all utilities be earthed to same
earthing electrode. Exception is only when it is not practicable.
But another utility offers this 'buried wire' solution to providing a
single point earth ground that will also provide better surge
Essential is that every utility be earthed to a common point for
Ideally you want a "single point ground" with the entry protectors for
CATV, phone, ... connected with a short wire to the earth electrode at
the power service. When the 'ground' at the house lifts from 'absolute'
ground with a large surge you want 'grounds' for phone, CATV. power to
lift together. Would the mast do that? Probably. Much better than the
water pipe unless there is a comparably short connection to the earth
electrode wire at the power service.
I have never seen a source that says an external buried wire between
phone NID and CATV entry and power service 'ground' will keep the
'ground' potential the same at all three - the basis of a "single point
ground". A ground rod is also required at the CATV entry.
Bud routinely forgets to see things that would expose his plug-in
protector as ineffective.
Earthing must accomplish two task - equipotential and conductivity.
To achieve equipotential beneath a building, then all earthing must be
'single point'. Some facilities only use an earth ground rod. Some
install earthing as demonstrated in
Others use far more serious earthing just to achieve a little better
earth ground (ie Ufer grounds). Some examples from those who want
effective protection rather than expensive 'magic boxes':
Curious how they understood a well proven technology that Bud has
never heard of. They are installing protection. Bud is promoting
grossly overpriced plug-in protectors that have no dedicated earthing.
My post, was about earthing, not plug-in suppressors.
Repeats what w_ previously posted without explaining how the external
wire provides a “single point ground” - as challenged in the quote at
In the US, Ufer (concrete encased electrode) grounds are required for
new construction with footings or foundations. They are actually a good
grounding electrode. Far better that ground rods.
Terry could install a Ufer ground. All he would have to do is tear out
about 20 feet of his basement wall and footing and reinstall it. Is
that what you are suggesting.
And nobody is talking about a “magic box”. Since you insist on dragging
in plug–in suppressors, the IEEE guide says that if you do not have a
single point ground "the only effective way of protecting the equipment
is to use a multiport protector."
If w_ was not a troll he would admit Ufer grounds have been in many of
The troll’s favorite topic again.
For reliable information on surges and surge protection see the IEEE
Or the NIST guide at:
The IEEE guide explains plug-in suppressors work by CLAMPING the voltage
on all wires (signal and power) to the common ground at the suppressor.
Plug-in suppressors do not work primarily by earthing The guide
explains earthing occurs elsewhere. (Read the guide starting pdf page 40).
Both guides say plug-in suppressors are effective.
w_ has never found a link that says plug-in suppressors are not effective.
Ask the cable company to move the ground to the mast. Make sure your
electric service is grounded - may require adding 2 ground rods. Make
sure the water pipes are bonded.
For reliable information on surges and surge protection see the IEEE at:
Or the NIST guide at:
The NEC requires now, as it has required for a very long time, that a
metal underground water service pipe, 10 feet or longer underground, be
used as a grounding electrode for an electrical service. Bonding can use
a little different methods and is required when the service pipe is less
than 10 foot metal underground.
When used as shown in the IEEE and NIST guides, and manufacturers
literature, plug-in surge suppressors protect connected equipment.
Protected equipment is all connected to the same suppressor or external
wires, including phone, CATV, go through the suppressor.
Both guides recognize earthing, single point ground, service panel
suppressors and plug-in suppressors.
If you don’t have a single point ground a service panel suppressor does
not always protect.
The point of a “single point ground” is that ground wires from phone,
CATV, ... protectors connect with short wires to the earthing wire at
the power service. If there is a strong surge the ‘ground’ at the house
will lift from ‘absolute’ ground. The whole point is that the ‘grounds’
for the power, phone, CATV, ... lift together. Francois Martzloff, who
wrote the NIST guide, has written "the impedance of the grounding system
to 'true earth' is far less important than the integrity of the bonding
of the various parts of the grounding system."
While you are at it, read the responses.
Urban metal underground water supply systems have very low resistances
to ground. More limited systems are likely to be a lot better than
ground rods, the likely electrode that Terry will use. A “good” ground
rod for the NEC is a 25 ohms to ground – very poor. Usually 2 rods are
used and the resistance doesn’t have to be measured.
Starting with the 2005 NEC a Ufer ground/concrete encased electrode is
also required for new construction with concrete foundations. Ufer is
also a good ground and makes a good “supplemental” electrode.
Connection to metal water pipes has for quite a while been required to
be within 5 feet of the entrance to the building.
The short connection is to the earthing wire at the power service.
The only change has been the requirement to add a “supplemental”
electrode in the case that the metal water service pipe was replaced by
plastic, as happened to Terry.
As is well known to some on this newsgroup, w_ has some bizarre ideas.
I had almost the same blowup; the cable
modem, router and motherboard .... plus
my scanner got it too. My cable was
grounded at the NE corner of the building
to a ground rod, which the cable company
put in many years ago. The current
thinking is to ground the cable to the
electric meter. My electric meter is at
other end of the building wrapped around
by a deck. So, I called Comcast
and ask that they come out to properly
ground my cable service. Before they
came, I pulled up a few key boards on
the decking and added a couple of pull
wires from the area of the electric
meter, to the outside edges of the deck.
the tech came, he said, "well, I was
going to tell you that I'd have to
due to the large amount of work, but you
did it all, so I'll do it!" They ran a new
drop to the pedestal, added a cable box
next to the electric meter and ground
it all to the electric meter. LOL,
shortly after I canceled my cable modem as
fast DSL was available and, in a few
weeks I will be canceling Comcast in favor
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.