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#40597 07/28/04 10:02 PM
Joined: Dec 2002
Posts: 4
Junior Member
Do metal drain pipes need to be bonded to water supply pipes? What happens if a hot wire touches the metal drain pipe while I'm taking a shower? Because my water supply piping is grounded to my panel and ground rod, and the drain pipes are electrically isolated (rubber boot near point where it exits the house), couldn't I be electrocuted while taking a shower if current flows through the shower water, or would a breaker trip before I received a shock? Should I install bonding between the drain piping and the water supply piping? What does the NEC say about this? The drain pipe is connected to my tub with a rubber washer, and does not appear to be electrically connected to the water supply pipes. I've called two electricians who tell me this is nothing to worry about.
Thanks for any advice.

#40598 07/29/04 07:20 AM
Joined: Dec 2003
Posts: 751
Unless murder was intended, just how could your metal drain pipes become energized? What appliances are metallicly connected to the drain? If any are, they would have a EGC to bond them anyway. So long as your home is wired to code, and your wife still loves you, you cannot be electrocuted in the shower.

However, if your water pipe is not grounded, then there may be some current flow through the water pipe, through the water flowing over your body, through your body, then into the drain pipe to ground. A pleasant sensation will creep all over your skin, making you glad to be alive. It will envigorate your whole day!

Maybe not.

#40599 07/29/04 08:02 AM
Joined: Dec 2000
Posts: 4,291
My drain lines at home are all metallic. I've got brass tailpieces and traps, and cast iron (with old oakum & lead joints) waste piping. These are connected to a vitreous clay (read ungrounded) sewer lateral.

Contact on the system anywhere to an energized conductor would cause the drain system to become energized. The only saving grace that I've got is that the kitchen sink is made of cast iron, and might (or might not) have continuity to ground, either through contact with the garbage disposal, or contact with the water supply.

I think "electrical dummy" has a point...S

#40600 07/29/04 09:02 AM
Joined: May 2004
Posts: 73
In code class, we had a similar discussion concerning the hot water piping, with the isolation at the water heater, the use of plastic piping, and the use of non-metallic sinks. I have copper and cast iron drains in my house and rely heavily on the garbage disposal being grounded properly. Seems like the same principal of the proper grounding of the furnace circuit grounding the gas piping. Does this mean we're relying on the plumber and tinner to do our grounding? Are we supposed to check? Who pays? Stay tuned for the answers to these and other important questions.

#40601 07/29/04 06:36 PM
Joined: Apr 2002
Posts: 2,527
I suppose it centers around “interior metal piping likely to become energized”. Looks like the 2002 NEC includes it for separately-derived system bonding.

#40602 07/29/04 07:00 PM
Joined: Mar 2004
Posts: 193
I would be interested to know if anyone has heard or read of this before.
My motto is:
"If you can think of it, it has probably happened to someone before"

"If common sense was common, everyone would have it"-not sure, someone here

#40603 07/29/04 07:08 PM
Joined: Sep 2002
Posts: 931
Likes: 1
If you have cast iron soil piping useing "No-Hub" bands each section of pipe would be isolated /insulated from each other due to the rubber coupling and the way it is designed,that statement would not apply to the old lead and oakum joints. If One had copper DWV piping I would sleep better if it were bonded.

[This message has been edited by NORCAL (edited 07-29-2004).]

#40604 07/30/04 03:03 AM
Joined: Feb 2004
Posts: 1,438
Ok... I have some first hand experience here...

I had a call from a customer that was having the wacky unbalanced voltage syndrome along with being "shocked in the shower"... early 60's home, everything looks normal for the era of build.. Panel grounding solely on the cold water.... So Cal Edison's neutral was loose up on the pole... All the unbalanced load was (trying) to shunt through the cold water system & thus the difference of potential between the fresh water system & the sewer system was shocking the bejeezus out of the homeowner! [Linked Image] Poco fixed their connection & the problems went away.. But I sunk 2 ground rods while I was there, just in case.....


#40605 07/30/04 06:26 AM
Joined: Dec 2000
Posts: 4,291
Fiberglass tubs, porcelain lavatories, plastic kitchen sink.
Metal drains, nonmetallic lateral.
Flying splices, open j-boxes, romex chewing rats.

I don't think it's at all far-fetched.

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