Dan_Jacobson@ATT.COM (05/24/91)
Outside there is a big lightning storm. Should I risk the brief moments of a closed liquid circuit between me and the plumbing system by using the restroom? [I need to know soon.]
jjhoxsey@vela.acs.oakland.edu (Kuros) (05/24/91)
In article <1991May23.223109.19908@cbfsb.att.com> Dan_Jacobson@ihlpz.ATT.COM writes: >Outside there is a big lightning storm. Should I risk the brief >moments of a closed liquid circuit between me and the plumbing system >by using the restroom? [I need to know soon.] I dunno -- can't you just "hold it"? I do recall reading in Cecil Adams "The Straight Dope." that there was once a dead man found in the subway tunnels who had died from electrocution. The evidence was clear-but I'm sure you don't want to hear about it-that the man was urinating on the third rail of the subway system. For you rural propellor-heads out there, the third rail is the electrical supply for the subwar car(s) that is very much like a normal train track rail. Now whether or not your plumbing is safe.... Besides, isn't it known that you shouldn't be on the computer during an electrical storm? %) -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- "Even I must take a break from | jjhoxsey@vela.acs.oakland.edu (Kuros) wackiness occasionally." | Gogo Dodo | The IRC Silly Knight (w/rubber chicken) -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
rbrink@hubcap.clemson.edu (Rick Brink) (05/24/91)
From article <6556@vela.acs.oakland.edu>, by jjhoxsey@vela.acs.oakland.edu (Kuros): > >>Outside there is a big lightning storm. Should I risk the brief >>moments of a closed liquid circuit between me and the plumbing system >>by using the restroom? [I need to know soon.] > > I do recall reading in Cecil Adams "The Straight Dope." that there was > once a dead man found in the subway tunnels who had died from > electrocution. The evidence was clear-but I'm sure you don't want to > hear about it-that the man was urinating on the third rail of the > subway system. For you rural propellor-heads out there, the third > rail is the electrical supply for the subwar car(s) that is very much > like a normal train track rail. > Some time you urban nerdians are in the rural country side, try urinating on an electrified cattle fence. You'll live through the experience, but you'll gain some respect for propellor-heads who know enough not to do it...
mkaminsk@cvbnet.prime.com (mailhost) (05/24/91)
From article <1991May23.223109.19908@cbfsb.att.com>, by Dan_Jacobson@ATT.COM: > Outside there is a big lightning storm. Should I risk the brief > moments of a closed liquid circuit between me and the plumbing system > by using the restroom? [I need to know soon.] Talk about a painful shock :-) I think you're risking more by posting this message over the phone line. To say nothing about possible damage to your hard disks. So, turn off your computer and go. Mark B. Kaminsky mkaminsk@cvbnet.prime.com Computervision/Prime Computer, Bedford, Massachusetts, USA
imp@solbourne.com (Warner Losh) (05/25/91)
Correct me if I'm wrong here, but isn't the metal plumbing in your house grounded? Is that why the house's electrical system is sometimes grounded to the plumbing? And since it is grounded, wouldn't it have a zero or near zero potential? So there is no problem. However, other examples that have been given assume the "object" is much different than ground potential. Warner -- Warner Losh imp@Solbourne.COM The question to everyone's answer is usually asked from within
jtchew@csa2.lbl.gov (JOSEPH T CHEW) (05/25/91)
>Correct me if I'm wrong here, but isn't the metal plumbing in your >house grounded? In theory, yes. The cold-water system is often regarded as one of the best grounds in the house. However, gotta watch the broad statements. The drain/waste/vent plumbing, which includes the waste stack below the toilet and the vent pipe above it, is trending towards ABS, a rugged plastic, in many areas. Also, metal D/W/V pipes are often joined by rubber connectors. The cold water supply might also include plastic (PVC) links, so the only grounding there, at some points, would be by virtue of the water's conductivity. Various systems are often mixed by do-it-yourselfers or even contractors without caring about electrical matters. Significantly, my cold and hot water pipes and gas pipe were bonded together (at the water heater) at the behest of the electrical inspector (who regarded the D/W/V pipes as a don't-care), not of the plumbing inspector. So here's a scenario: the best lightning target on a roof might well be a piece of metal D/W/V pipe going down to a toilet, but thereafter grounded only by a spark + water path through the toilet and into the cold-water system. And/or other good grounds nearby. A weenie roast, so to speak, seems improbable but plausible. Remember that at a few tens of kiloamperes, fractional-ohm differences get really significant. --Joe "Just another personal opinion from the People's Republic of Berkeley"
jfa0522@hertz.njit.edu (john f andrews ece) (05/26/91)
In article <13568@dog.ee.lbl.gov> jtchew@csa2.lbl.gov writes: >>Correct me if I'm wrong here, but isn't the metal plumbing in your >>house grounded? > >In theory, yes. The cold-water system is often regarded as one of >the best grounds in the house. > >However, gotta watch the broad statements. The drain/waste/vent >plumbing, which includes the waste stack below the toilet and the vent >pipe above it, is trending towards ABS, a rugged plastic, in many areas. >Also, metal D/W/V pipes are often joined by rubber connectors. > >The cold water supply might also include plastic (PVC) links, so the >only grounding there, at some points, would be by virtue of the water's >conductivity. > >Various systems are often mixed by do-it-yourselfers or even contractors >without caring about electrical matters. Significantly, my cold and >hot water pipes and gas pipe were bonded together (at the water heater) >at the behest of the electrical inspector (who regarded the D/W/V pipes >as a don't-care), not of the plumbing inspector. > >So here's a scenario: the best lightning target on a roof might well >be a piece of metal D/W/V pipe going down to a toilet, but thereafter >grounded only by a spark + water path through the toilet and into the >cold-water system. And/or other good grounds nearby. A weenie roast, >so to speak, seems improbable but plausible. > >Remember that at a few tens of kiloamperes, fractional-ohm differences >get really significant. > >--Joe >"Just another personal opinion from the People's Republic of Berkeley" I suspect it is more likely that only the drainage conduits may be PVC, as it is still (last I heard) not considered safe enough for the drinking supply. That would mean that as you stand, barefoot, on the ceramic tile floor, making glorious contact with the water basin, you may be at risk. Of course, what are you doing barefoot on a grounded floor anyway??? (Can anyone quantitatively compare impedance of rest-of-water-in-pipes to appendage impedance? That's the ticket ;-)
henry@zoo.toronto.edu (Henry Spencer) (05/26/91)
In article <1991May24.210108.9982@solbourne.com> imp@solbourne.com (Warner Losh) writes: >Correct me if I'm wrong here, but isn't the metal plumbing in your >house grounded? ... Apart from the problem of non-metallic plumbing, which others have mentioned, it is important to realize that just because one end of a conductor is grounded doesn't mean the other end is at ground. "All points on a wire are at the same potential" is a useful rule of thumb when dealing with small currents and low frequencies. Here we are talking about very large currents with plenty of high-frequency components; the rules change. However, it seems unlikely that there would be problems unless there was a lightning strike on the house or very close to it. If that happens, you probably have other things to worry about. Lightning doesn't have to follow conductors at all; it got to you by punching through hundreds or thousands of meters of a very good insulator. -- "We're thinking about upgrading from | Henry Spencer @ U of Toronto Zoology SunOS 4.1.1 to SunOS 3.5." | henry@zoo.toronto.edu utzoo!henry
clewis@ferret.ocunix.on.ca (Chris Lewis) (05/26/91)
In article <13568@dog.ee.lbl.gov> jtchew@csa2.lbl.gov writes: >>Correct me if I'm wrong here, but isn't the metal plumbing in your >>house grounded? >Remember that at a few tens of kiloamperes, fractional-ohm differences >get really significant. Or, put another way, at a few tens of kiloamperes, there ain't no such thing as a good ground. (Well, perhaps a superconductor a few square feet in cross-section... ;-) -- Chris Lewis, Phone: (613) 832-0541, Domain: clewis@ferret.ocunix.on.ca UUCP: ...!cunews!latour!ecicrl!clewis; Ferret Mailing List: ferret-request@eci386; Psroff (not Adobe Transcript) enquiries: psroff-request@eci386 or Canada 416-832-0541. Psroff 3.0 in c.s.u soon!
chidsey@smoke.brl.mil (Irving Chidsey) (05/28/91)
In article <1991May24.210108.9982@solbourne.com> imp@solbourne.com (Warner Losh) writes: > >Correct me if I'm wrong here, but isn't the metal plumbing in your >house grounded? Is that why the house's electrical system is >sometimes grounded to the plumbing? And since it is grounded, >wouldn't it have a zero or near zero potential? So there is no >problem. However, other examples that have been given assume the >"object" is much different than ground potential. > >Warner Losh imp@Solbourne.COM Plumbing is not a reliable ground! PVC tubing does not conduct appreciable ammounts of electricity. Even copper pipe may have insulating sections put in to stop ground currents from causing electrolysis. The problem is not whether you are grounded or not, it is whether you are in a significant ground path that happens to conduct electricity. A college friend was milking the cows during a thunderstorm. Lightning hit about 100 metres away. That cow never ever again let him milk her. He had to call his mother for that one cow. She was sure it was his fault! Irv -- I do not have signature authority. I am not authorized to sign anything. I am not authorized to commit the BRL, the DA, the DOD, or the US Government to anything, not even by implication. They do not tell me what their policy is. They may not have one. Irving L. Chidsey <chidsey@brl.mil>