Copper pipe electrolysis from touching galvanized steel?
Q. I recently had a 1/2" TYPE L HMP flexible copper pipe that sprung a leak, unfortunately it was inside the wall going up to the second floor. After splicing the pipe where it was leaking another spot started leaking. I noticed inside the pipe a bunch of green "blobs" & the outside of this (HOT) water pipe a lot cleaner than the other pipe (COLD) that would have been put in at the same time, 20-25 years ago I'm guessing. I did notice one spot where the copper pipe was touching an old galvanized pipe seemed to be wet and green. Could there have been some electrolysis going on that caused this pipe to start getting finer than pin hole leaks & how much damage might have been done to the rest of the plumbing if that is the case?
THANK YOU FOR YOUR HELP,Alex H
do-it-myself-er - Cedar Rapids , Iowa
A. Copper pipes can corrode in at least three different ways, but the differences are quite technical. I would suggest that the corrosion could be induced by a galvanic couple caused by contact with the galvanised pipe and this results in an induced local anodic polarisation of the copper pipe. I would normally expect such a failure to occur where the two pipes come into contact, but if this point is dry, no corrosion will occur and the effects of the galvanised pipe will be transmitted onto the copper pipe where it will react in a more favourable wet environment. Your photograph clearly shows the green copper salts on the inside of the failed straight pipe, so it must have been in an area where the copper is oxidised and failed. The propensity for copper pipes to fail is related to how the pipe was made, the local water composition and the environment it is used in. I would suggest there may be other not be other problems with your copper pipes, as there has already been a failure of an induced polarity, but if there are other non-compatible pipes in contact with each other, there could be a repeat of this. It may be wise to ask a plumber to check your system out.
R&D practical scientist
The Pheasantries - Chesham, U.K.
Q. I was told by a local plumber that electrolysis can occur in copper pipes when the hot water heating system is part of a forced hot water boiler system. The solution is to put nylon fittings between the copper connections and the galvanized boiler system so as to prevent any electrolysis action from taking place in the copper pipes running throughout the building. I would like to get other opinions since this is an expensive fix and it takes a long time to determine whether the fix in fact works.Dan W
property management - Juneau, Alaska
A. It is the right advise, Dan. For galvanic corrosion to occur you need a metallic circuit and an electrolyte circuit. If you break the conductive metal circuit between the copper and galvanized pipe, galvanic corrosion ("electrolysis")" does not occur. This is not to say that no form of corrosion will ever occur though.
Ted Mooney, P.E. RET
Brick, New Jersey
A. Copper pipe failure began to occur approximately eight years after completion of a new home in Brewster Co. Texas. The leaks were always in the cold line.
A split-core ammeter revealed a slight current flow between the steel gas pipe and the hot side of the copper system. No current could be detected between the cold copper pipe and the hot, or the steel gas line. This led me to conclude that the cold line was acting as a sacrificial anode between the other two while absorbing all voltage drop.
No electrical bonding could be found.
My solution was to isolate the steel line (which included some galvanized parts), from the copper system with a PVC adapter.
Current flow cannot now be detected unless a jumper is placed between the steel and copper.
Is the problem solved? I don't know! What can be said is that there is no further measurable evidence of electrolytic activity in this particular system.Sam D
- Alpine, Texas
A. As others have mentioned, there are three different ways for holes to develop in a copper line, and I have seen all three.
A typical trade mark of electrolysis is pit on the inside of the pipe where the electrical currant has actually eaten away at the piping, this doesn't sound like what is going on.
Another way is corrosion from the outside, normally when the piping in in a damp location with high acid soils, or even in an unsealed sleeve (copper run inside another pipe, usually PVC, and normally from the meter to the house). This is evidenced by pitting on the outside of the pipe.
The last one I have come across, and am still researching, is what it sounds like this gentleman has. It typically will have build-up on the inside of the piping and will often times leave large "blobs" of build up. I don't know what this is for sure, but I do know it isn't electrolysis, and it has nothing to do with water that is too clean (mentioned on another website as a possible answer). I think it has to do with the water quality to a certain degree, but I think it may be the molecular structure not the chemicals used. I think the buildup is a protectant for a "micro-atmosphere" high in maybe hydrogen. But I could be wrong, I am still researching this. I will post any further findings.Jereme Grisenti
plumbing - Blountville, Tennessee
Q. If we were to rivet or otherwise attach a copper sleeve to galvanized chimney pipe, would this cause the galvanized pipe to fail? We have fireplace chimneys on the beach. we have several copper clad chimneys that are doing well, but the maker went out of business. Now we have only galvanized pipe to work with and the outside of it corroding causes an eye sore.Bryan Malt
- San Diego, California
Q. This is a piggy back question.
Three 1/2 inch copper pipes running from my basement to the Laundry room one floor above show the same kind of erosion as the picture accompanying the original question. In each case the green copper salts and pin holes developed where the pipes pass through the floor. You can see the leaking water from below but not from the laundry room level.
After one of two plumbers to replace one of the leaky pipes stated that at one point he felt a very mild electrically shock, I had an electrician check the system. The electrician said he could not find a problem. The electrician checked the system before and after the plumber felt the shock. We could not duplicate the shock with the plumber or the electrician.
The plumber reinstalled the three pipes and wrapped the new pipes in electrical tape at the point where the pipes go through the floor.
Since we have not yet found a source of electrical charge would it be prudent to ground the copper line to an unused galvanized pipe so any current would flow to the unused galvanized pipe? Any help would be appreciated.
- Stafford, Virginia
Q. When copper pipes are plastered over into walls do they need to be protected from corrosion either by cement or plaster?Mrs M Bridger
Homeowner - Steyning, West Sussex, England
Q. I have a brick wall in my bathroom and want to cut a groove in the brick run the copper pipe inside and cement it back up. Will this have a long term effect on the pipe
designer - Toronto, Canada
Q. I have some questions regarding electrolysis, or galvanic corrosion between the copper and galvanized water pipes in my house. The house in on a municipal system and it is my understanding that acidic or soft water is not a problem in my area.
I have extremely low pressure in the upstairs bathrooms, and moderately low on the main floor kitchen. In my basement I have galvanized pipes coming in from the street, they supply the hot water heater, and they run the hot water for a few feet beyond the tank. At one point they are connected directly to copper pipes which take the hot and cold supply upstairs to the bathrooms.
I intend to replace the galvanized pipe, but I am trying to decide whether or not to replace the copper pipes going upstairs, and as well the hot water heater.
To make this decision I need to understand a little more about what is going on with the electrolysis. Before discussing the ramifications with the hot water heater, I have the following questions:
1. Where the galvanized and copper connect in the basement, does the electrolysis happen only locally? It seems that the electrons would travel only within the magnetic field created by the metals and therefore only affect the pipes within about a foot or so of the connection. Or, since the water exists through all the pipes, does the electrolysis affect the copper all the way to the upstairs bathrooms?
2. Once the galvanized pipe is removed, will the electrolysis cease? (I understand that new copper and old copper will also create electrolysis but I assume this condition is not as severe.)
3. I understand why galvanized pipe corrodes when coupled with copper but I don't understand why it is that the galvanized pipe becomes filled with gunk on the inside and restricts flow, I would think the corroding would make it get slightly wider on the inside, not more narrow.
4. If I remove the galvanized pipe, can I clean out the remaining copper pipe to make sure there is no corrosive material setting in them? How is this performed?
As far as the hot water heater is concerned, galvanized pipe feeds it and takes the water out of it, however, there is copper flexible tubing that actually connects directly to it. I assume this means the heater has corrosive material in it and will likely not last as long. If I leave the existing heater in place and wait for it to fail, will it contaminate any new piping that I put in?
Also, if I run the new copper water service through the front yard within a few feet of the gas line will this cause electrolysis? If yes, will it affect the pipes inside the house or just in the front yard? Which pipe will get holes and which will narrow? Can I insulate the copper to prevent this?
buyer, hobbyist - Seattle, Washington
July 13, 2008
Q. I have type k copper coming from the main to the shutoff in the house. after reporting a leak it was dug up to be repaired and all was found was a pipe with walls that have thinned considerably and covered in grooves resembling termite damage on wood. it was also riddled with pinholes.
the ground for my electrical is connected to this pipe. could that be a possible cause. please help. there other houses in the area that have had there lines replaced twice in the last 20 years.
hobbyist - conne river, Newfoundland, Canada
A. Where I work they were having problems with the copper pipes. The anode rods in the water storage tanks had been all wore down. Plumbers found the electrical system grounding rod had been disconnected & everything was grounding through the plumbing, causing the problems. You might want to check but I think it is a code violation now to ground through your plumbing only.Alex Hatfield
- Cedar Rapids, Iowa
August 30, 2008
Q. I have a problem identical to to the lead in this thread. Green spots on rigid type L 1/2 in copper pipe with water seepage. This 14+ ft run of pipe is leading from my gas fired hot water heater (after a few short copper fittings) across the drywall finished basement ceiling to a T that feeds hot water to most of the house. I noticed a small spot of mold on the ceiling, cut it open and found this pipe with green spots like the picture above and two of the spots (at different ends of this one section of pipe) have water seepage. There are several other copper pipes , cold water and feeds for hot water heating that have no green spots,(only this one length of hot water has the spots) and also a flexible gas line in the same bay. My fix is to replace this entire length. A difficult job for me, tight spaces overhead, and hope there are no other bad pipe in the house. Please confirm the cause of this. Is it likely to be elsewhere or reoccur?David Goldman
- W Milford, New Jersey
A. In response to the gentleman who experienced a leak on a 1/2 copper pipe and then he split it exposing this thick green blob running on the inside for some unknown length. well from dealing with similar repairs and from years of experience in the field this green corrosion that you are talking about stands far from electrolysis. this green gunk/blob is what we use to solder/sweat our copper pipes with better known as FLUX this product is applied to the outside of the copper pipe once it has been cleaned and reamed. putting to much flux on the pipe and fitting will cause the excess to flow into the pipe and will settle on the inside of the pipe until the system gets energized and water flows flushing out the excess flux. if it was not flushed out and was left as is; guess what? call your plumber.....thanks.Armando Olvera
- Costa Mesa, California
September 14, 2008
Q. Within the last 9 weeks we have called the plumber 3 times regarding a 4 ft. section of hot water copper piping. Each time a pinhole sealing leak about 4-6 feet away from a recently replaced(5 months ago that our plumber installed) electric hot water heater. After replacing 2 inch copper pipe sections at a time we finely asked him to change a length of pipe but, only last night we developed another leak, a foot over from the new pipe, closer to the water heater. Our house is 15 years old and we use city water. The leaky pipe had green discoloration at the leak points. The plumber says this problem could be expected in this area in homes using well water after about 20 years due to the highly acidic soil but we use city water and our pipes are in the sealing. He's suggesting we may need to replace all of our pipes but it seems strange that the leaks are all near the water heater. Could the water heater be faulty or it's installation be the problem?Chris McQuillen
homeowner - Crescent City, California
A. Hi, Chris. I'd be pretty confident that is has to do with something electrical rather than well water. I think I'd call an electrician rather than calling the plumber again.
Ted Mooney, P.E. RET
Brick, New Jersey
September 30, 2008
Q. can a copper water line be spliced to an existing galvanized water pipe line?Keith Medved
- Dyer, Indiana
A. Hi, Keith. When you transition from one kind of metal pipe to another, the correct thing to do is to use dielectric unions =>
These are unions that include a plastic insulator so there is no metal-to-metal contact. I'm not saying that this is always done, but it is the right way to insure that there can be no galvanic corrosion.