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PLUMBING SYSTEM INSPECT DIAGNOSE REPAIR
AGE of PLUMBING MATERIALS & FIXTURES
AIR DISCHARGE at FAUCETS, FIXTURES
ANTI SCALD VALVES
ANODES & DIP TUBES on WATER HEATERS
BACKUP PREVENTION, SEPTIC
BACKUP PREVENTION, SEWER LINE
BACKWATER VALVES, SEWER LINE
BATH & KITCHEN DESIGN GUIDE
CHEMICAL CONTAMINANTS in WATER
CHEMICAL ODOR SOURCES
CHLORINE IN DRINKING WATER
CLOGGED DRAIN DIAGNOSIS & REPAIR
DEBRIS in WATER SUPPLY, Water Heater
DEPTH of SEPTIC TANK
DRAIN & SEWER PIPING
FAUCETS & CONTROLS, KITCHEN & BATH
FAUCETS, OUTDOOR HOSE BIBBS
FLOOD DAMAGE ASSESSMENT, SAFETY & CLEANUP
FLOOR DRAIN / TRAP ODORS
FLUSHOMETER VALVES for TOILETS URINALS
GAS PIPING, VALVES, CONTROLS
GALVANIC SCALE & METAL CORROSION
HARD WATER - SOFTENERS
HEAT TAPES, Heat, Insulation prevent Freeze-Up
LEAD POISONING HAZARDS GUIDE
LEAD IN DRINKING WATER, HOW to REDUCE
METHANE GAS SOURCES
MIXING / ANTI-SCALD VALVES
MUNICIPAL WATER PRESSURE IMPROVEMENTS
NOISE / SOUND DIAGNOSIS & CURE
ODORS GASES SMELLS, DIAGNOSIS & CURE
ODORS IN WATER
ODORS, SEPTIC or SEWER
ODORS SEWER GAS in COLD WEATHER
ODORS, SULPHUR SMELL SOURCES
ANIMAL or URINE ODOR SOURCE DETECTION
PIPING IN BUILDINGS, Clogs Leaks Types
PLUMBING FIXTURES, KITCHEN, BATH
PLUMBING NOISE TRANSMISSION CONTROL
PLUMBING VENT DEFINITIONS & CODES
PLUMBING VENT DEFECTS & NOISES
PUMPS USED in BUILDINGS
PUMPS, WATER REPAIR
RELIEF VALVE LEAKS
RELIEF VALVE, TP VALVE, BOILER
RELIEF VALVE, TP VALVE, STEAM BOILER
RELIEF VALVE, WATER HEATER
RELIEF VALVE, WATER TANK
REPAIR BURST LEAKY PIPES
METHANE GAS HAZARDS
SEPTIC SYSTEM INSPECT DIAGNOSE REPAIR
SHUTOFF VALVE LOCATION, USE
SULPHUR & SEWER GAS SMELL SOURCES
SWEATING (CONDENSATION) on PIPES, TANKS
TOILETS, INSPECT, INSTALL, REPAIR
WATER, WELLS, WATER TANKS: TESTING GUIDE
WATER PRESSURE LOSS DIAGNOSIS & REPAIR
WATER PUMPS & TANKS
WATER SOFTENERS & CONDITIONERS
WATER SOURCE ALTERNATIVES
WATER SUPPLY & DRAIN PIPING
WATER SHUTOFF VALVE LOCATION, USE
WATER SHUTOFF VALVE, WELL PUMP
WATER TESTS, CONTAMINANTS, TREATMENT
WELLS CISTERNS & SPRINGS
WINTERIZE A BUILDING
Dielectric plumbing connectors:
Tthis article describes the building code and practical requirements for a dielectric fitting when connecting copper piping to steel pipes or steel fittings such as at the top of a water heater.
We explain the effect of galvanic corrosion at copper to steel pipe connections and we include notes on the recommendation for a jumper wire across dielectric fittings or water meteres to assure that a plumging system is properly grounded for electrical safety.
The FAQs section of this article includes questions & answers about the dielectric fitting debate, concerns for fitting leakage, and notes that a brass nipple may be permitted to connect copper to steel in some building code jurisdictons.
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In most jurisdictions plumbing codes require the use of a dielectric fitting when joining steel piping to copper or other metals; some plumbing jurisdictions permit use of a 6-inch brass nipple in this location as an alternative to diaelectric fittings. Why?
When connecting iron or galvanized iron pipes to copper in buildings, often galvanic corrosion and ultimately plumbing leaks will occur at the meeting of these two dissimilar metals.
Using a diaelectric fitting or an approved brass fitting to connect these two metals, or more commonly, using plastic or bronze fittings at the joint between these two metals will avoid future corrosion and leaks.
The photo (left) shows a galvanized iron union used to connect copper to galvanized iron. In the upper image you can just make out the black bronze ring built into this plumbing connector to avoid corrosion where the copper presses against the galvanized iron.
OPINION: in our experience having inspected thousands of homes, we find that original plumbing in older homes rarely made use of a dielectric fitting or even a brass nipple at copper to iron or steel piping - and corrosion is often found at one or several such connections.
In new construction where more careful code compliance and enforcement are applied, dielectric or brass fittings are more common. Some plumbers opine that "lined" nipples sold by some manufacturers for water heater hookup reduce the galvanic corrosion risk at those connections. - Ed.
Water chemistry affects the rate of galvanic corrosion
How do we explain that in some buildings we see direct copper-to-iron pipe connections with no corrosion? Luck? Maybe.
But the corrosivity of the water is probably a factor in how rapidly copper-to-galvanized pipe connections will corrode and leak.
Spelling note that may help some searches: it's not dialectic pipe fittings, but dielectric pipe fittings.
Teflon tape or pipe dope may slow the rate of galvanic corrosion
Another reason we may not always see rapid galvanic corrosion at copper to steel pipe connections is the use of teflon tape (or less-so, pipe dope or sealant compound) that provides a thin non-metallic contact surface between the two dissimilar metals.
Nevertheless, both to comply with plumbing codes and to avoid leaky water pipes, use an approved diaelectric coupling or an approved brass nipple (if local codes permit) when connecting copper to steel pipes or fittings or when connecting copper pipe to the steel fitting at a water heater.
More about the galvanic scale and corrosion between dissimilar metals is at GALVANIC SCALE & METAL CORROSION.
Jumper wires are required to ground plumbing across dielectric fittings
At ELECTRICAL GROUND SYSTEM INSPECTION we discuss the need for a jumper wire around interruptions in the metal piping system, such as where a diaelect4ric fitting is installed or where a water meter interrupts continuity.
As Carson Dunlop's sketch shows at (A), if the building plumbing includes dielectric fittings or non-conductive sections of piping (such as plastic piping) then the building plumbing system may not be safely grounded.
Spelling note that may help some searches: it's not dialectic pipe fittings, but dielectric pipe fittings.
Manufacturers of Dielectric Unions / Fittings
Discussion & debate about dielectric fittings
READER OPINION: On your web page ELECTRICAL GROUND SYSTEM INSPECTION, near the bottom, is a question "jumper across dielectric fittings is asking for galvanic corrosion." Your reply to the question concludes with the comment "Also I am nor sure which jumper you saw, but connecting a ground between similar metals ought not create the concern youncite."
That same page includes an illustration [shown just above in this article - Ed] showing this very connection: copper pipe joined to galvanized pipe through a dielectric union with a jumper wire around the dielectric union.
The unilateral recommendation that this connection should be jumpered is concerning: if the union is required to protect the integrity of the pipe and whatever fluid (or gas?) flows inside it, then jumpering around the union defeats that protection and may lead to accelerated failure of the pipe. I think additional consideration on this topic is warranted. Regards, G.H. 7/10/2013
Thank you GH for the comment, and for being interested in this episodic debate about using dielectric fittings and jumper wires around them as well as understanding the effects of galvanic corrosion.
While I'm certainly not an expert on the topic, I think the assumption that galvanic corrosion will occur only at the point of contact between the two metals is flawed. Consider for example the "lasagna cell" battery: an uncoated steel baking pan containing a lasagna (or other salty food serving as electrolyte) and covered with conventional aluminum foil. Holes will form through the aluminum foil in the places where it contacts the lasagna -- not around the edges where the foil is touching the steel.
There's no way it could have corroded so quickly without a boost from something like galvanic corrosion. But it didn't corrode at a connection between dissimilar metals; it was the side of the elbow that was eaten out. Anyway, I think he mentioned that beyond the elbow (continuing underground) was PVC pipe so there probably was no dissimilar connection in that area at all.
If not so, I suppose we'd be using brass or bronze couplers or unions to join the pipes and skip the business with the plastic isolator in the dielectric union. I believe your experience (not seeing corrosion at the location of a jumper around a dielectric union) supports my suggestion that the corrosion is likely to happen somewhere out of sight -- specifically, at a point where the steel pipe contacts an electrolyte (something wet, probably soil).
I appreciate the discussion but it seems we disagree about the locus of galvanic corrosion in plumbing systems and perhaps you didn't know that building codes require both dielectric fittings (or in some locales a brass nipple) connecting copper to steel pipes in a building as well as jumper wires around dielectric fittings when needed to assure safe electrical grounding of the plumbing system.
The jumper wire around a dielectric fitting, properly connected with approved (typically bronze) clamps to the copper and steel piping and a copper ground jumper will not itself promote corrosion at the pipe connection nor nearby.
Plumbing texts as well as field experience point out that corrosion occurs at and/or very close to (micros to millimeters) the point of contact between dissimilar metals that are further apart on the galvanic scale, such as copper and steel. Long-standing and successful plumbing practice was to connect via an intermediate metal such as brass - as the galvanic corrosion problem does not appear at, for example a copper to brass connection (there are hundreds of millions of such connections in both plumbing and heating systems today).
Example Code Citations for the Requirement for Dielectric Connectors Between Copper & Steel Pipes
Section 316 of the California Plumbing Code is amended by adding Subsection 316.2.5 to read as follows:
Other building citation code sources where the requirement for a dialectric plumbing fitting is cited:
Continue reading at GALVANIC SCALE & METAL CORROSION or select a topic from the More Reading links shown below.
Suggested citation for this web page
Green link shows where you are in this article series.
Frequently Asked Questions (FAQs)
Question: pinhole in copper water pipe under the slab
I have a home that is 7 yrs old in Burleson Tx. We are on a co-op water supply. I recently had a pin hole in my copper water pipe under the slap. I though it was the water but had the water dept lab test my water and all was normal. I then read about electrolysis could cause this. I do have a ground on my water pipe and a rod out side my main. I checked whit a meter and I do have continuity between the main panel and my plumbing and my gas pipe to the hot water. can this possible cause my plumbing to fail?
The water has been ruled out so it has to be something else the pin hole was from the inside out and my house water connections are green and blue. need some help bad. I did disconnect the one ground off the plumbing when I read about the electroylis. Please advise.
Reply: Causes of pinholing in copper water supply or drain piping
If you do nothing but fix the pipe and the problem never recurs I'd suspect the pipe itself. But if it were me, I'd also have a licensed electrician check that the home's grounding and neutral systems are properly wired, that the grounding electrodes are properly sized and installed, and that there are no stray currents on the neutral system nor shorts or leaks in the wiring system (an AFCI or GFCI can help detect these too).
Question: follow-up on pinhole leaks in copper piping traced to bad (grounded) neutral connections at the utility transformer
Dan, concerning the pin hole pipe leak and all the green and blue plumbing from Oct. 19 & 21, 2011. I have seen this before and traced it to bad grounded (neutral) connections at the utility transformers or tap boxes causing all the neutral loads to be carried on the grounding system such as the copper plumbing.
I even seen it in one house but show the signs of trouble in a neighbors house because of a common city water pipe. This situation eats the copper water piping from the inside out and can cause green/blue water color, usually the first sign.
Also, these pin hole can develop because of excessive flux being used before sweating. The excess flux lays in the bottom of the pipe and corrodes the copper, hence pin holes on the bottom only. - Rod, electrical contractor, 8/1/12
Question: jumper across dielectric fittings is asking for galvanic corrosion
You show a jumper wire across a dielectric plumbing connection (between copper & galvanized pipe). This will promote galvanic corrosion & make the dielectric connection pointless. Instead of at the connection the corrosion will now take place inside the galvanized pipe near the jumper wire clamp.
Grounding the plumbing does not make a house safer. It places half an electrical circuit through out the house. This increases the likelihood of connecting that circuit with some current. - Galvanic 9/20/12
The jumper wire across a dielectric fitting does not cause corrosion in copper to steel piping connections provided it is properly made using approved connectors (typically brass or bronze clamps).
If we don't jump across a non-conductive dielectric fitting on water piping then the water piping is not grounded. By current NEC, metal piping may not be used as a grounding conductor, but metal water piping in contact with the earth for a length of ten feet or more, that piping is indeed connected to the electrical ground system.
For protection from lightning and possibly leakage from a high voltage transformer, the current National Electrical Code (NEC) requires two grounding electrodes at a building. If one of these is water piping it is tested and must show less than 25 ohms of resistance to earth.
Current NEC Citations on grounding water piping
Typically, pinholing in copper piping that is traced to an electrical grounding problem (electrolysis) is, if we exclude neutral/ground wiring errors, traced to inadequate local grounding electrodes.
Thanks for the interesting comment. I'm not sure where your surmise takes us, since there are both code and basic safety reasons for grounding house plumbing. Also I am nor sure which jumper you saw, but connecting a ground between similar metals ought not create the concern youncite. Can you give us a citation or article to review?
We ground building water piping for electrical safety for the occupants, not to provide an additional electrical ground path
The reason people ground in-building plumbing is not to provide an additional grounding conductor in a building but to ground the plumbing. Picture someone knocking a toaster into a stainless steel sink or into any sink with a metal drain and drain piping. If the sink and piping are grounded the fuse or breaker will blow. If not, the system is waiting to electrocute the building occupant when s/he touches the live water/toaster in the sink and perhaps a nearby metal faucet, radiator, or other component that is ultimately connected to earth.
Incidentally, as we discuss pinholing and bad neutral connections, keep in mind that the return path for current in a building's electrical system is not intended to be primarily through the building's local grounding electrodes. Rather it is on the neutral wire that is connected back to the pole transformer.
See LOST NEUTRAL Shocks Homeowner for details of what can happen when this connection is not made or goes bad.
Question: electrolysis corrosion problems after a ground system change
(Aug 24, 2014) Eric Schemanske said:
If the installer used a listed grounding system bonding clamp then its composition was intended to avoid corrosion due to electrolysis.
Usually the installer also includes a jumper around the water meter to assure continuity of grounding of the piping system.
I would be looking for a different electrical problem first as ruling it out is important. There may be stray voltage on your electrical system's neutral circuit or ground circuit from a short somewhere in the electrical panel or building wiring.
(Oct 28, 2014) Jason said:
We have a situation where steel piping is being connected to a copper tube heating coil both on the steam supply and condensate return without any dielectric isolation.
Lucky, but still it'd have been good practice; steam condensate is in fact quite corrosive.
28 Feb 2015 Anonymous said:
Take a look at GALVANIC SCALE & METAL CORROSION for a clear explanation of this.
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