w_tom wrote:
Irresponsible to connect wall receptacle ground to a water
pipe. A wet human in a shower, bath, or touching water in a
sink is at greatest risk. And you would dump electricity into
those pipes? Shame on you. It is safer to not ground at all
rather than connect to water pipes. Even the code does not
permit this type connection any more. The only electrical
connection to water pipes is to remove electricity from those
pipes. Never dump electricity into water pipes.

Numerous reasons to never connect AC receptacle ground to
water pipes. Electricity in those pipes is more hazardous
than an outlet without safety ground. Sounds as if previous
owners replaced all two wire receptacles with three wire
receptacles without the necessary safety ground. Therefore
those screws would have no safety ground connection. These
receptacles are only safe (and legal) if powered through a
GFCI. And GFCI was one of two possible solutions provided in
another post.

Meanwhile, any recommendation to connect safety ground to
cold water pipes only creates a potentially greater hazard.

Ron Tock wrote:

That little screw that holds the outlet cover on should be grounded.
You could attach to that. Or a cold water pipe.

w-tom
I realize that we may disagree on this but since the US NEC specifically
requires the use of underground metal water piping as part of a
building's grounding electrode system don't you think it would be
clearer to say "interior metal water piping" when saying metal water
piping should not be used as a ground for an electrical system. The
code specifically permits the equipment grounding conductor that is
installed as a retrofit ground to run to any electrode of the grounding
electrode system vis..

[VII. Methods of Equipment Grounding
250.130 Equipment Grounding Conductor Connections.
Equipment grounding conductor connections at the source of separately
derived systems shall be made in accordance with 250.30(A)(1). Equipment
grounding conductor connections at service equipment shall be made as
indicated in 250.130(A) or (B). For replacement of non–grounding-type
receptacles with grounding-type receptacles and for branch-circuit
extensions only in existing installations that do not have an equipment
grounding conductor in the branch circuit, connections shall be
permitted as indicated in 250.130(C).
(C) Nongrounding Receptacle Replacement or Branch Circuit Extensions.
The equipment grounding conductor of a grounding-type receptacle or a
branch-circuit extension shall be permitted to be connected to any of
the following:
(1) Any accessible point on the grounding electrode system as described
in 250.50
(2) Any accessible point on the grounding electrode conductor
(3) The equipment grounding terminal bar within the enclosure where the
branch circuit for the receptacle or branch circuit originates
(4) For grounded systems, the grounded service conductor within the
service equipment enclosure
(5) For ungrounded systems, the grounding terminal bar within the
service equipment enclosure(copyright 2002 National Fire Protection
Association)]

The point you are making is quite valid. The interior metallic piping
system must not be used as an equipment grounding or bonding conductor.
Having said that I have to take issue with the statement that "any
recommendation to connect safety ground to cold water pipes only creates
a potentially greater hazard." I realize that this is a fine point but
I believe it is important enough to be clear. The US NEC does not offer
any option. When an underground metal water pipe that is twenty or more
feet in length is available on the premise then it must be used as a
grounding electrode vis..

[250.50 Grounding Electrode System.
If available on the premises at each building or structure served, each
item in 250.52(A)(1) through (A)(6) shall be bonded together to form the
grounding electrode system. Where none of these electrodes are
available, one or more of the electrodes specified in 250.52(A)(4)
through (A)(7) shall be installed and used.
250.52 Grounding Electrodes.
(A) Electrodes Permitted for Grounding.
(1) Metal Underground Water Pipe. A metal underground water pipe in
direct contact with the earth for 3.0 m (10 ft) or more (including any
metal well casing effectively bonded to the pipe) and electrically
continuous (or made electrically continuous by bonding around insulating
joints or insulating pipe) to the points of connection of the grounding
electrode conductor and the bonding conductors. Interior metal water
piping located more than 1.52 m (5 ft) from the point of entrance to the
building shall not be used as a part of the grounding electrode system
or as a conductor to interconnect electrodes that are part of the
grounding electrode system. (copyright 2002 National Fire Protection
Association)]

Please note how carefully the Code Making Panel differentiated between
interior and underground water piping.
--
Tom H