Pitting in Copper Pipe

Zman

I recently bisected this pipe on a domestic water recirc system which has me scratching my head.

• The building is 21 years old.
  
• The copper is 2" type "L" made in USA
  
• The system is running at about 130 degrees.
  
• PH is low 7's
  
• TDS shows moderate hard water
  
• The original circ was significantly oversized and was replaced ~3 years ago. It had a pretty flat curve on top. I suspect it was flowing ~4-5 ft/sec.
  
• The new circ is appropriately sized but the system design is making balancing a challenge.
  
• This chunk of pipe is just after a 90 and had been repaired once in the past with a press-fitting.
  
• The eroded pockets are not consistently on the top or bottom of the pipe.
  
• It is possible that the steel building framing touched the pipe in the areas affected. I did not remove the pipe myself.
  

Any thoughts?

EBEBRATT-Ed

I don.t know but flux in cold water that doesn't wash away can be an issue

EdTheHeaterMan

I'd take the copper in the top pic and carefully flatten it out, sign it, and put it in a frame. Then see how much you get at an art auction.

It Beautifully represents the irony if man's quest for power in a state of damp solitude against the raging flow of mineral and liquidity in today's society.

Larry Weingarten

Hello, I see both erosion corrosion and pitting corrosion. The erosion would be from the big pump. About the pitting, a question: Is there manganese in the water? A good resource for problems like this is the Copper Development Association: https://search.proquest.com/copper/results/ACB2017D0E9F4E02PQ/1?accountid=26849
I wouldn't expect that touching steel framing would have any effect on the copper (aside from abrasion) unless it allowed some current flow, but even then, random pitting wouldn't be the result.
Yours, Larry

mattmia2

Didn't @DanHolohan have a problem similar to this:
https://heatinghelp.com/blog/a-copper-mystery/

Zman

That scenario is a close fit. I believe those failures invoked some sort sediment setting in the bottom of the pipe. Either ferrous or some sort of chemical compound. The ones I am looking at happen all over the pipe, not just the bottom.

hot_rod

I had a job where the electrician had all the galvanized flex wiring conduit lying on the copper water piping and it developed pin holes after about 3 years. Actually black spots everywhere the flex was in contact with the copper, pin holes in the same locations.

So you have slightly aggressive water, and have had excessive recirculation velocity in the past?
Un-reamed copper can add to pin holes especially if they are near fittings.
Also pitting can be caused by stray current, which could be galvanize and moist cooper, a galvanic cell. Put penny and a galvanized roofing nail in the water and clamp on your volt meter. Steel and copper will also set up a weak electrolysis cell, in presence of and electrolyte.
Usually a meter between the tube and an earth ground will show stray current.
Any electrical devices grounded to the copper tube, like the phone system? If you find any wiring ground to the copper, remove and put your meter in series, Same way you find stray current draining your car battery

And it could be a combination of things.

Ph is a bit low, might put some cartridges to boost that and coat the piping like Denver Water started doing.

Also TDS and hardness are not exactly the same, TDS is a measure of waters conductivity. Hardness testers are looking at scaling minerals like calcium and magnesium. Mountain or mine shaft water is usually hard water. Hard water tends to add a protective coating in the tube and protects it.
Is there a softener involved? It is possible to have soft water with high TDS. A softness tester may show low GPG, but TDS could still be high.

I agree the CDA has volumes on pin hole causes and preventions.