OK yoy experts (especially Bob W. if he's still alive),
My foreman griped today about copper lines touching metal studs and
cast iron drains. He said it'd cause electrolysis.
While I think it's a matter of good workmanship (not to mention noise
issues), I disagree that this causes electrolysis. My understanding is
that fresh water must actually flow between the dissimilar metals. Am I
wrong or right?
Sorry Mike, but all it has to do is touch.
It's the physical contact and the flow of electrons passing from one metal
(or liquid) to another. Each metal comes differently charged with electrons
and protons. The act of touching allows the metal with a deficiency of
electrons to strip away the metal that has more.
Voila! The battle is on.....:>)
You say; I believe. That's been the basis of our relationship.
But clear this up, if you don't mind. If it's just contact, then why
is it OK to screw copper DWV into cast iron tapped tees, and why is to
OK to screw copper into steel pipes on hydronic heating systems?
Can we ask questions? or do we just guess away.
If we can ask what you observed on your visit...
Was there an outward sign of something dumb, like water hooked to the gas
line? or did the installation look ok on the surface?
Did the restaurant have gas heat and if so did it work? or was it full of
water too? If the whole gas system was full of water and someone had not
changed something in the system then I would think that the gas control on
the HWH had Failed in some bizarre way.
Yes, of course you can ask questions. I re-read my story above and one thing
that I didn't make clear was that the store was functioning normal the
previous business day.
There was no apparent cross connections which was why I asked if there had
been any repairmen from any craft in the store in the previous couple of
weeks. The only gas was to the water heater and the cooking line. The water
heater was of course completely shut down as was the fryers. The mechanical
valves on the burners allowed water to stream out when they were opened
which to this day was one of the strangest things I've ever seen.
The obvious first step is to confirm no mechanical cross connections
After being there for about half an hour and seeing it with my own eyes I
was seriously considering calling a priest.:>)
I checked the gas meter and water meter for anything that appeared as recent
excavations. There were none.
But you're getting warmer......
This story is directly related to Mike's original question in this thread.
OK, so the water main and gas main were buried touching each other? I
am having a hard time seeing how the water pressure would have made it
into the gas line, but I guess I've see stranger things happen.
You're so close now that I'm gonna' go ahead tell the whole story because
someone guessing what actually happened is very unlikely.
After eliminating any mechanical cross connections by physically observing
every inch of the gas line above grade I had to turn my attention to the
service line. There was a catch basin (storm sewer) in the back by the drive
through lane. I noticed a small trail of water on the expansion joint at the
basin and after dragging my finger across it I was able to determine that
the flow was coming out from the outside of the box and then immediately
draining right back into the box. Had the storm system not been draining the
original leak they might have seen the water leak before the next part of
this weird story could have taken place. I then shut of the main water entry
and looked at the water meter and the 1/10 dial was spinning like crazy,
telling me that there was an apparent leak in the water service between the
meter and the building.
I then ordered an air hammer rig and some extra help and we shut down the
drive through and began breaking concrete. Using the same finger dragging
trick I determined the direction from where the water was coming from and
followed it back to the leak. Once it was obvious where the leak was at we
turned the water off and began digging down and was amazed at what I
discovered. There was a point where the gas line and the water line had to
cross to get to their ultimate destinations. The gas service was schedule 40
wrapped steel and the water service line was type "K" soft copper. The water
line was about 6" deeper than the gas line and exactly at the point where
they crossed someone had allowed a 16 penny nail to be backfilled touching
the copper water service line. The ensuing electrolysis ate a hole in the
copper and it began spraying and that water spray CUT A SLOT in the STEEL
gas service line and the weight and forced pressure ultimately was able to
push water up the gas line and out the gas stove burners a good 3 or 4 feet
higher than the point of rupture.
I still have that 16 penny nail to this day as a reminder on one of the
strangest calls I ever had to go on.
You win Bob,
It might have taken me a Day to figure it was outside that far. Where it cut
thru the Gas line, was it on the building side of the meter? or the city
If it was on the city side, what did it do to the gas meter?
Both meters were at the street and both service lines were on the owner or
private side of the meters so there was no culpability on the part of the
Both lines were installed by the plumbing contractor that did the original
project. That said, I wouldn't say that I blame the plumber for not noticing
a nail during a backfill operation but I do blame the plumber for not
wrapping or isolating the copper and protecting it from contact by
I have read their propaganda before. You have to consider the source.
They are "copper.org" and their mission is to positively represent copper as
the "ultimate" material for any and everything.
The CDA Mission
"The Copper Development Association Inc., CDA, is the market development,
engineering and information services arm of the copper industry, chartered
to enhance and expand markets for copper and its alloys in North America."
The first paragraph is a freakin' joke:
"Electrolysis is an overused and misused term when applied to copper tube.
True electrolysis, or electrolytic corrosion, as it is more properly
designated with regard to piping, is caused by an imposed (external) stray
DC current and virtually ceased to occur with the disappearance of the
trolley-car that was powered by high amperage DC current."
They have _zero_ credibility. Try this one instead:
(It is simple and easy to understand)
Bob, can you give me a citation for what you just wrote?
My understanding has always been that there needs to be an electrolyte
present for galvanic corrosion take place, and that metals with
dissimilar galvanic potentials can safely be placed in contact with each
other in a dry environment, or even one where the liquid present is non
coductive, like for example lubricating oil.
I see too many examples of things like steel pins in brass hinges
lasting for decades to believe that very much damage occurs, and what
about steel shafts in bronze bearings?
I should have been more clear. Water is all that is necessary and that
automatically comes with all plumbing systems from condensation. Both hot
and cold supply systems will have condensation because of temperature
variation between the internal and external enviroments. So, the "act of
touching" applies in all copper domestic water supply situations that are
relevant to this discussion. But I suppose you could create some non-world
reality condition for the purposes of an experiment.
There are several important factors to consider when it comes to galvanic
corrosion. The metals of course are obvious, but we have to consider the
environment and the relative mass of each metal and the relative size of
contact and the relative position each holds in the galvanic series.
Even the building's electrical system is a factor.
There was some of this info on my previous posting with this web site:
All that said, you can look at what appears to be identical situations such
as a copper pipe against a metal stud in two different buildings and one is
severely damaged and the other looks brand new. Ditto for two different
water heaters where someone screwed copper male adapters directly into the
tanks. As plumbers we can only control so many factors and thus the one we
can is to ensure we don't allow contact of dissimilar metals that are known
to cause problems such as steel to copper. This usually applies mostly in
the commercial field where if we read our spec books they almost always
include the requirement that there be no physical contact between dissimilar
Now you have me worried ( Love the rest of the Thread, BTW)
So on my hot water heater It has Brass fittings, we have the copper lines
going up close to the heater, then have the braded stainless hose with the 2
female fittings. One end goes to the heater the other to the plumbing.
The braided stainless fittings look like they are chrome plated, but what
kind of metal is it?
All of them I have used are stainless and I do not use them on water
If you are going to use a flex then use a standard 3/4x18 waterflex. It's
made of brass/copper and it is dielectric.
So you dont recommend the Braided Stainless on water heaters? These are the
ones that are in the water heater section. You prefer the copper looking
Oh, this is for an outside application too. The heater is a Takagi outdoor
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