Corrosion of copper water line?

[ACtrafficengr]

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/

 

[bigbranddan]

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

 

[Pump2005]

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.

 

[bimr]

"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

 

[dicksewerrat]

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.

http://WWW.amlinereast.com

 

[coloeng]

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.