Sealing Copper piping interior???

Hi,

I haven't visited this website for awhile, but I have had quite a few slab leaks, and I am now in the midst of another one. I had it checked a few months ago, and when the plumbers jackhammered, it had sealed itself, and now is back. They originally said they thought the foundation was overpoured and it is in that overpour so that they might not be able to get to it.

I think Duraflow monitors these websites, because they somehow sent me an email. I talked to them, but have not really done further research. Have you?

Nancy

I too had a hot water domestic water leak 5 years ago and haven't had one since. I knew I would eventually get another and so when I was deciding on a new floor to install on the remodel we just finished, I decided to look closer at why the leak was occuring.

In a nutshell, the copper pipe is corroding due to an anodic/cathodic reaction between the hot and cold water pipes. The pipes run in the dirt just beneath the slab and the corrosion happens in the pipe that touches the dirt. Here is a more detailed information on what actually happens:

http://www.sescocp.com/tutorial.php

Can you explain where your leak occured? Was it in the pipe laying on the soil?

It turns out that it is common practice to protect pipes in the soil using a method called "cathodic protection". You can think of this of transferring the corrosion from your domestic pipes to a sacrificial anode. This is exactly what I had done 2 months ago. Large municipalities and companies with expensive piping routinely use cathodic protection to protect their assets. I would much rather keep the domestic pipes I have now rather than tear up my walls and route the pipes overhead .

I can furnish the name and contact info for the company that came to my house to analyze the soil/pipe conditions. Contact me at lynndrake2001ATyahooDOTcom.

Given my soil resistivity, they installed 5 Magnesium sacrificial anodes in the ground next to my house and electrically connected them to my domestic water pipes (just a copper wire hooked to my hosebib outside). Although this does not reverse the corrosion that has been occuring for the past 50 years, it will stop any further corrosion.

Assuming that all Eichlers have their domestic pipes just below the slab, I would think that all domstic pipes will eventually spring some leaks. Those with low resistivitiy soils might see failure faster than those who don't.

Here is some about cathodic protection:

http://www.matcor.com/
http://www.cpdesigncenter.com/
http://www.corrosion-doctors.org/SoilCorrosion/Frames.htm
http://www.corrpro.com/

/ Lynn Drake in Palo Alto

Hello,
Unfortunately, the cathodic reaction between hot and cold pipes is only part of the problem. I have seen many sections of copper pipes that have been excavated that have several pinholes from electrolysis. The relationship to the direct buried copper pipes and the direct buried EMT (electrical metallic tubing) conduit, and the fact that that conduit is rotting away below the slab (EMT has not been rated for direct burial for about 35-40 years because of this). The result is that copper wires with TW insulation are direct buried under the slab with no conduit, and the soil is likely drawing electrons (it is, after all, an excellent ground, or point where there are 0 volts). If this condition occurs near direct buried domestic supply lines, failure is unavoidable. My Advice- leave the slab alone, re-route your plumbing to the roof (it caN eventually be relocated beneath the roof membrane (foam , tar and gravel, etc) and on top of the ceiling planks when you re-roof, without too much trouble. Good luck.

Thank you for your inputs to my inquiry about floor leaks. I have concerns about rerouting. My larger bathroom has been recently tiled, including the walls. I guess they could go through the paneling in the bedroom next to the bathroom (I hope). I also have a mirrored dining room wall in the dining room next to the kitchen sink. I am hoping if I went the rerouting route, they could go up the space that seems to exist between the dining room paneling and the kitchen wall. That particular wall is also tiled. Also, I have a foam roof, and it is very difficult to get people to come out and do repair work on an existing foam roof. I've had a couple of rough estimates of around $8,000.

It would be around between $3000 and $4000 to do the epoxy treatment in the pipe if this is a viable solution. I am still looking into it. I was hoping someone else had researched it.

Lynn,

I copied and pasted your email address to send you an email, but received messages that it wasn't a viable email address. I tried using the DOTcom and .com, as well as @ for AT, but to no avail. I don't know what I am doing wrong.

Nancy

P.S. You can reach me at: [email protected].

Renman-

Perhaps you can lend some insight into what you have seen with domestic pipe failure in Eichlers but I believe that most if not all have their domestic pipes buried in the soil under the slab. Is this correct? If so, I think this domestic water pipe failure in Eichlers will happen with greater frequency. Eventually all of them will fail.

I am a materials engineer and it bothered me why this corrosion occurs. This led me to the solution of applying cathodic protection to the pipes. Luckily I found a corrosion engineering company that was professional and routinely fixes problems like this one. I think Eichler owners should know there is alternative to rerouting their pipes or just waiting for the next failure.

I asked the corrosion engineer who installed the CP system to comment on this message and here is what he said:

"The fact that their is an electrical conduit with copper electrical lines inside has absolutely no effect on the insitu copper water lines. These power lines are carrying AC current which will not cause a pipeline to corrode to the effect of a DC current. In most homes it is common to ground out your electrical sytem to your copper waterlines. With this being said the presence of the electrical conduit is not the factor in these 'pin sized' holes developing on the copper.

The corrosion is occuring from an "anodic-cathodic" reaction that is existing below ground. DC current that is flowing through the ground will be received by the pipeline in the 'cathodic' area and at the location in which it is discharged, the 'anodic' area, the corrosion will occur. There are several factors that will lead to the corrosion of your copper water lines. Some of them being:

        - Soil Resistivity
        - Material Imperfections in the copper
        - Proximity of the cold and hot water lines to each other
        - Foreign sources of Current, such as PG&E gas lines which are protected

Corrosion is a naturally occuring process and can be combated through the use of Cathodic Protection. In a nutshell, with Cathodic Protection you are installing a 'sacraficial anode' which will corrode instead of your copper water line. Cathodic Protection is a very common practice and is becoming more about asset protection because we all know how much it costs to keep repairing something. Most systems are designed with a minimum of a 20 year life span; however, most systems will keep protecting after that."

Best regards, Lynn Drake
Palo Alto

Lynn,
Your engineer specialist certainly has an interesting point re. AC versus DC current characteristics. Where are the sacrificial materials best located? How much pipe can best be protected with what type of installation?

Randy- everything that is connected to the hosebib (an outdoor faucet) will be protected which includes in my case the hot and cold water lines and the radiant pipes (these are physically connected to the water line). The radiant pipes have negligible corrosion because they are embeded in high resistivity concrete and do not see the corrosive environment that the pipes laid in soil see.

The sacrificial anodes were buried outside in the dirt along the alley side of my house (the 8 ft wide area along the 4 bedrooms). The chosen location came down to a practical matter- what is most accessible without digging up a concrete walkway or lawn but at the same time maximizing the protection of the pipes.

/Lynn