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Corrosion of copper water line?

Corrosion of copper water line?

Corrosion of copper water line?

(OP)
A village water department suffered a failure of a water service line installed under one of our highway projects roughly 8 years ago. It's a 1" lateral that serves a local diner.

The copper line was heavily pitted and perforated from the inside out. The copper on the inside looks almost silver, as if it was plated with some other metal.

It was backfilled with course sand meeting (or supposedly meeting) NYSDOT specs for select granular fill.

Based on this article, I suppose the first steps might be to test for sulfates, chlorides, stray electric currents, etc.

If anyone has any additional suggestions, I'd really appreciate it. This is, as you might expect from my handle, a bit out of my area of expertise.

     Maybe the tyranny of Murphy is the penalty for hubris.  - http://xkcd.com/319/
 

RE: Corrosion of copper water line?

Hard to say without seeing the tubing.

A couple of observations:

The 1-Inch pipe size is too small for a restaurant. Would expect that a high water velocity would be contributing to the corrosion problem.

The location of the tubing under the road would indicate that the tubing is exposed to road salt. Is the pitting on the exterior or interior? Other metallic piping systems that are located near roads have also experience corrosion due to road salts.

Have other water services experienced corrosion? If not, there is lttle reason to expect that the water quality is the problem.

RE: Corrosion of copper water line?

(OP)
Thanks for the reply.

Looking at the pipe again, it could well be erosion from velocity and turbulence, not corrosion:


    [li] I was wrong - the pipe i.d. is ~0.7, not 1". Even though it's a tiny diner, but they'd still use a lot more water than a residence.
    [li] the inlet end was cut square, with a burr on the inside, not smoothed or reamed in any way.
    [li] The pitting is from the inside out, with only a bit of oxidation on the copper.
I've attached a photo. For scale, that's 1/4 graph paper.

We'll have to check the plans, and see if it was a mistake by the designer or the contractor.

 

     Maybe the tyranny of Murphy is the penalty for hubris.  - http://xkcd.com/319/
 

RE: Corrosion of copper water line?

You appear to have the typical erosion/corrosion of turbulence and velocity. See the attachment.

RE: Corrosion of copper water line?

(OP)
bimr, it looks like you've had the same attachment issues I did. I ended up pasting the URL directly into the message text box, rather than using the "step 3" box.

RE: Corrosion of copper water line?

Am curious what is coupling or fitting partly out of view? Any chance "silver" area that looks like plating of other metal IS other metal (solder)? [As to "erosion"  silver interior surface appearance, as well as fluid velocity limitations I notied in the linked douments, for copper pipes are interesting. While copper pipe is much harder than most of the plastics, e.g. as can be observed in Figure 8 of the site at http://www.calce.umd.edu/TSFA/Hardness_ad_.htm and other references, it is much softer than e.g. steel or ductile iron etc.]  

 

RE: Corrosion of copper water line?

(OP)
It's a compression fitting coming off the T in the main.

RE: Corrosion of copper water line?

I think it is a combination of velocity and a sligthly acid water . A compression fitting should NEVER be buried. Use flared fittings. My guess would be that the diner needs at least a 1" tap and 1 1/4" line. May have to talk to the local water authority now that there is some consumption history for the proper size.  

Richard A. Cornelius, P.E.
WWW.amlinereast.com

RE: Corrosion of copper water line?

Does the restaurant have flush-o-matics? (tank-less toilet and urinals) even if you have low overall consumption, a flush-o-matic pulls 20 to 30 gpm for the first second or two of the flush.
Minimum size for just one flush-o-matic is 1.25".  Add in a commercial 90 second cycle time dishwasher and you have some very high velocities.

If you replaced the line like for like, then require the restaurant to install a large hydro pneumatic tank to reduce the surge velocities or replace the flush-o-matics with tank type toilets.

Hydrae  

RE: Corrosion of copper water line?

The black indication on the surface says sulphur to me.

rmw

RE: Corrosion of copper water line?

(OP)
Apparently, the same thing happened on a residential line, also.

RE: Corrosion of copper water line?

Have you put an clamp-on amp meter around the copper service line?
If one location has a bad ground with a damaged element in the electric hot water heater, it will corrode service lines for hundreds of feet in the area.

You may have to wait until the hot water heater cycles on to see the stray current.  

Other cases show up as the electric service uses the water line as the neutral due to bad earth ground and lacking an adequate service line neutral.  The current will follow the water line to the neighbors earth grounds and neutrals to close the circuit.

Hydrae  

RE: Corrosion of copper water line?

Don't believe that stray current has anything to do with your corrosion problem.

The electrical code has required for some time that if the electrical service is grounded to a water pipe, an additional earth ground is required. In addition, metallic hot water pipes and cold water pipes are required to be bonded together at the water heater.

Your picture shows corrosion on the interior of the tubing. Note that stray current corrosion will occur on the outside of the tubing, not the inside. That is because the current actually travels on the outer surface of the wire (or tube) not on the inside of the wire.

Here is an additional reference for erosion corrosion:

"As has been emphasized, copper water tube is highly dependent upon the formation and maintenance of a protective film on the inside to provide a long trouble free service life. The film is not hard and abrasion resistant, but rather soft and easily damaged."

"An even more conservative recommendation limiting water velocity to a maximum of 4 fps has been published by the National Association of Corrosion Engineers (NACE)."

http://www.wssc.dst.md.us/copperpipe/copperpipewp.cfm



 

RE: Corrosion of copper water line?

When you say the "same thing happened" also on a (one would think more normal flow) residential service, do you mean a similar perforation in roughly or exactly the same location/goose-neck? area immediately off the main? This brings me to a couple other questions in additions to those already asked, has anyone looked at the external or internal condition (or measured wall thicknesses et.) at other locations of the services in question? [I ask these questions, of course, in that it might be argued (with regard to at least the internal erosion and/or corrosion theories) that roughly the same conditions might arguably exist to some extent/be contacting the inside of all areas as well]. What kind of main and specific type of corporation? connection to same is involved?

I once read that some Roman copper water pipe was found intact after 5,000 years of burial -- while I agree it is hard to tell much just from the picture, it would certainly appear however you had at least something going on here the Romans didn't have!  

RE: Corrosion of copper water line?

[Oops, in retrospect I don't think Rome as such, or even Romulus and Remus, were around that far back! -- very early and old copper pipes were probably in Egypt)

RE: Corrosion of copper water line?

My gut feel is low pH.  We see this a lot when people try and do whole house reverse osmosis which tends to leave a lower than neutral pH. Also with well water customers that have a low pH.

I would start with a water test.  Many overlook the LSI, langlier saturation index.

High chlorides can also cause pitting.  High chlorides even will pit 316 stainless steel pipe.  

Basically even if your pH is very close to neutral, such as 6.8 if you have low alkalinity and low hardness that can be very corrosive.  High velocities can make things worse.  

Even high pH and low alkalinity can be a problem.

Take a look at this EPA reference
http://www.epa.gov/nrmrl/wswrd/cr/corr_res_copper_ai2.html

Dan Saltsburg
Big Brand Water Filter

RE: Corrosion of copper water line?

dicksewerrat, do you have a link to information about compression fittings shouldn't be buried?  Unless we are putting a flare connection back together we use brass compression fittings exclusively for copper line repairs. Sounds like it would be an interesting read.

RE: Corrosion of copper water line?

"Compression fittings have become the most popular choice for underground copper water services in recent years, because of their high strength and ease of installation."

http://coppercanada.ca/publications/pub28e/28e-section3.html

Some plumbing codes prohibit compression fittings under concrete. However, in general, if the manufacturer of the device approves the installation, it is is an accepted practice.


"Flared joints and compression fittings shall not be installed underground except for water services, water meter yokes and stop box connections."

http://www.ilga.gov/commission/jcar/admincode/077/077008900C03400R.html


 

RE: Corrosion of copper water line?

Pump2005   I was a Utility inspector for 16 years. We used Type K copper and flares only. The plumbibg code later on allowed 'silver solder' for some buried 3" copper lines. Compression fittings can under duress pull out easier than flared fittings. I don't recall if this was City of Mpls Code or State Plumbing code.  But then this was also 1971 thru 1987.

Richard A. Cornelius, P.E.
WWW.amlinereast.com

RE: Corrosion of copper water line?

Compression fittings have come a long way since the 70's and 80's.  I was a plumber in the late 70's and never used a compression coupling underground because they were unreliable. Now they have a locking mechanism that is very effective in preventing pull-out.

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