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Ron The Plumber 02-25-2007 10:56 AM

Why is this?
A water heater that has a ground connected between the two pipes on this water heater, why would this be like that?

Is it needed?

jproffer 02-25-2007 11:14 AM

Looks like somewhere there is something grounded to a hot water line and they were trying to keep the connection back to the main water-line ground near the panel. They should have found a better way to ground their equipment IMHO.

Ron The Plumber 02-25-2007 11:17 AM

Thanks, will inform a member about this.

jwhite 02-25-2007 11:45 AM

That jumper is required by code to ground the hot water lines in the house. The main water pipe ground, bonds the cold water lines, but the fittings inside a water heater insulate the supply lines from the output lines to the rest of the house. The jumper bonds the two together.

Ron The Plumber 02-25-2007 11:59 AM


That jumper is required by code to ground the hot water lines in the house. The main water pipe ground, bonds the cold water lines, but the fittings inside a water heater insulate the supply lines from the output lines to the rest of the house. The jumper bonds the two together.
Ok thanks, this was a question that came up in the plumbing forum.

Maybe you can stop in and explain why the ground is there.

RippySkippy 02-27-2007 08:38 AM


Originally Posted by jwhite (Post 34726)
..but the fittings inside a water heater insulate the supply lines from the output lines to the rest of the house. The jumper bonds the two together.

Really? I wouldn't think there'd be a loss of continuity from a copper pipe (cold) connected to a metal tank connected to a copper pipe (hot)... Any chance you could cite the code chapter for this?


Stubbie 02-27-2007 03:40 PM

NEC 250.104(a) and the jumper is sized to table 250.122. Water heaters that have dielectric unions to which the copper pipe is connected to the steel tank are what the code worries about. These unions have an insulating bushing. Therefore you have no way to prove that the connection with the tank can carry the maximum fault that can be imposed. The unions are there to prevent the corrosive effect of copper and steel in direct contact with one another. A jumper usually #6 or #4 is required between the hot and cold lines. This insures bonding of the piping system to the service enclosure and grounded conductor. Without this you cannot rely on a breaker tripping on fault. The code requires the bonding jumper... this insures bonding of the piping system regardless of past,current or future installation methods. It also insures bonding if excessive corrosion degrades the connections at the tank when no unions are used.


jwhite 02-27-2007 06:02 PM

Yea what stubbie said.

Let me add that the code does not say that the hot water tank needs a jumper. It says that the water pipe system needs to be bonded.

In many areas the inspector is satisfied by the fact that most new faucets serve the same purpose since they do not have those kinds of fittings. The jumpers were first put in when most sinks and tubs had seperate spouts for the hot and cold.

The jumper can never be a bad idea, and for five bucks in material you can't go wrong installing it.

RippySkippy 02-27-2007 09:55 PM

That's what I like about this site...good info to be had. I don't know that I've seen the diaelectric unions on the water heaters I've that makes perfect sense, and I agree, $5 in material would be a good thing. Good to know...thanks!

See what you think of this... -- it's related to gounding on water neighbor was having issues with some circuits in his house...breakers tripping and other oddities...nothing really seemed to add up. His water main 1" copper coming into his house under the basement footing was serving as the main electrical panel ground.

When the main busted the ground was moved from the water pipe to a grounding rod near the service entrance...the copper pipes grounded to the new rod and the problems went away. Does that seem right? A person there during the main replacement said that in the right soil conditions, copper (I suspect that if anything it could be in the soil structure) will loose it's ability to act as a ground. I've always been skeptical...but since I'm not in the trades, I don't see that much in the way of oddities....


Stubbie 02-27-2007 11:55 PM

Probably didnt have a thing to do with his electrical system problems. You must first understand that the GEC system (grounding electrode conductor) and the EGC system (equipment grounding conductor) serve to different purposes. The gec system.. ig...metal water pipes and ground rods and other electrodes along with the connecting conductors bonding those electrodes to the grounded conductor (service neutral) in the service equipment (main disconnect) are in place for huge voltage events such as lightning and power surges. Low voltages 300 volts or less tend to not flow to earth unless it is the only path available. This is why the gec and the egc are bonded to the service neutral (grounded conductor) only at the main panel.
The egc is for human safety and provides the fault current path so breakers will trip. In a typical short circuit fault to ground the fault current travels the egc... ig ... bare wire in the romex or metal conduit back to the service neutral bar where bonding occurs with the grounded service conductor (neutral). It does not flow to the ground rod or water pipes at that point. It travels the service neutral to the center tap or xo of the serving transformer which is then earthed. This is because it provides a far lower impedance than the gec. This is what allows your breakers to trip as it accomodates the large flow of current that accompanies a short. Without massive current flow a breaker will not trip and therefore faults need a low impedance path to facilitate large amounts of current. If you were to open the service neutral making the only available fault path to the ground rod or water pipes or both it is likely that a breaker will never trip and all metal in contact with the fault will come to line voltage.
However the gec (water pipes and ground rods) will assist preventing equipment and propery damage in gigantic voltage events such as lightning where high voltage (thousands of volts and high amps) will travel to earth from the shear force of the emf.

Example: An electrical hot wire (ungrounded conductor) comes in contact with a hot water pipe after the hot water tank. The fault current travels the hot water pipe to the bonding jumper and travels to the cold water pipe. It then travels the cold water pipe to the point where the grounding electrode conductor is required to be clamped (bonded) to the cold water pipe (electrode) within 5 feet of where it enters the ground. It will not then travel the pipe to earth but will flow on the gec to the neutral bar and then out the service neutral due to the much lower impedance provided by that path. The breaker will trip and the circuit with the fault will deenergize. If that bond to the cold water pipe by the gec coming from the neutral bar in the main panel did not exist then bonding the metal piping system (hot to cold) of the dwelling would be ineffective in facilitating enough overcurrent to trip the breaker because the only fault path would be to earth via the water pipe. The impedance is too high to allow enough current flow. What you will end up with is a whole bunch of energized metal and a electrocution hazard will exist.
In the above screnario both the gec and the egc are sorta partners and this works due to effective bonding.

Hope this makes sense...kinda hard to get the longest chapter in the NEC into simple terms.

FYI...below is a dielectric union commonly used by plumbers to connect the copper pipes to the hot water tank..notice the red plastic bushing. The pipes are sweated to the brass end. Notice the corrosion on the connections to the tank in this thread. One of the reasons for the bonding jumper.

Also if a "main" metal water pipe exists and it is in contact with earth for at least 10 feet after it leaves the home it is required to be the primary grounding electrode. Ground rods are supplemental to it and at least one is usually required (if it meets the 25 ohm test).... if not then you must drive one more ground rod. If you dont have the test then 2 ground rods are required to supplement the water pipe electrode.

Your friend with the oddities would have been best suited to determine what breakers were tripping and begin troubleshooting at that point. You could remove the gec and egc entirely and your electrical system will function just fine. You just won't have safety (egc) or property (gec) protection. Both these systems are meant to not carry any current or serve any purpose unless a fault occurs or a huge voltage event effects your home. This of course assumes that the service neutral does not open.

**I would also like to point out that the hot water heater vent in this thread is in violation of plumbing codes. It has no degree of rise after leaving the hot water heater but is just a horizontal run. The 90 degree bend at the beginning is a no no.


rjniles 02-28-2007 07:54 AM

I hope you replaced that water heater ;-)

jwhite 02-28-2007 05:14 PM

the op was in the plumbing forum. Ron brought the question here for them. Yes this came up while the person was replacing the water tank, and wanted to know if to re-install that jumper.

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