Copper pipe corrosion under kitchen sink

[Darth Mau]

Hi plumbing community,

Hope one of you can shed any light on the following: inspection discovered the following copper pipe under kitchen sink with significant corrosion on the exterior. This is in a ~5 year old house and all other copper pipe are good and does not show the same corrosion. My questions are:

1. what is the function of this pipe as it comes out of the wall and back into the wall without apparent connections.
2. what could be the cause of such severe corrosion in a relatively new home? Is it indicative of bigger problem (say grounding problem, or water quality, etc)

Any advice appreciated!

 

[Rickyman]

1. I think it’s a loop for the refrigerator ice maker. So you can install a reverse osmosis system under the sink and have fresh ice and water at the fridge.
2. You either have a leak or the plumber didn’t wipe his flux after he soldered.

 

[Darth Mau]

Thank you Rickyman. For the cause, can I rule out leak if I don't see any visible water dripping our or under the pipe? Also, is it possible that it's simply caused by the moisture captured by white paint material covering the pipe (I am guessing the pipe could have been painted over or covered in paint material, and that trapped moist inside until eventually the paint material peeled off?)

 

[Geofd]

is this a slab house?????does the copper come out of the floor???? do you have hard water

 

[TomFOhio]

A lot of times the cleaners under a kitchen or bathroom sink will cause this. Like comet or something. It will do this to
chrome drain piping and make it look like its going to fall apart but its not.

 

[Jamesplumbing06]

From pic it’s hard to see if paint or not. But the thickest part of the crust is right on top of pipe. And directly under cold side of kitchen faucet. Could the old kitchen faucet have leaked onto the pipe for a long time then finally got changed and no one ever noticed that pipe? Grabbing straws could be thick paint. 220 grit paper and light pressure. See if it can clean off. If it’s calcium build up call a plumber and let him be ready for water.

 

[AAP]

Do you have a soap dispenser above? Strange how it’s where the electrical outlet is. Mineral reaction to an electrical field? Can you rule that out? Soapy water inn your hands running down the sprayer handle and down the beaded hose? Better yet a reaction to the dissimilar metals in contact (copper supply/braided stainless steel spray hose) do you have a water softener?

 

[Geofd]

Do you have a soap dispenser above? Strange how it’s where the electrical outlet is. Mineral reaction to an electrical field? Can you rule that out? Soapy water inn your hands running down the sprayer handle and down the beaded hose? Better yet a reaction to the dissimilar metals in contact (copper supply/braided stainless steel spray hose) do you have a water softener?

i thought the same thing about the electrolosis maybe a galvi hanger behind the wall or its touching a steel heat pipe somewhere

 

[chiraldude]

Scrape off all the crud and get down to clean copper. Then keep an eye on it to see if this is actively corroding. If the copper is clean and stays dry it shouldn't corrode.

Cleaning chemicals can cause this. Anything with chlorine bleach or acid based (CLR, rust remover, etc...) stored under there?

 

[Mr_David]

Clean it off with some fine grit sand cloth.

1. I think it’s a loop for the refrigerator ice maker. So you can install a reverse osmosis system under the sink and have fresh ice and water at the fridge.
.

Probably right about being a loop to Refrigerator

You never want to run a reverse osmosis filtered water through copper tubing.
RO actually removes most all minerals from water.
Due to lack of minerals the water will attract the copper and remove molecules of copper over time .

Here is a something I found with a simple web search
Q: Why are we supposed to avoid using copper tubing for Reverse Osmosis systems?

A: The issue with reverse osmosis (RO) systems is that they reduce pH and -- because of a reduction in the buffering afforded by alkalinity -- increase corrosion (of most metal piping, including copper). The typical RO unit will remove 90 percent of salts in water, so you can assume the water salts concentration of the purified water would be about 1/10th of the content in the feed water. The aggressiveness of this purified water toward the materials into which it comes into contact is a function of its purity -- the higher the purity, the more its aggressiveness. All RO systems reduce pH (usually by 1 to 2 units).

One thought is to add a calcite filter (calcite is calcium carbonate and it elevates pH by gradually dissolving) to raise pH after the RO unit. Although in some respects, adding salt back to the water after going to all that trouble to take the salt out seems a little crazy. Can you use plastic or stainless tubing? This would eliminate the concern about corrosion. Brass tubing is significantly better than copper from the standpoint of resisting low pH corrosion, but you run the risk of lead leaching. As a rule of thumb, plastic tubing is your best recommendation in connecting an RO to a fixture. And while there may be some copper in a refrigerator, for example, it's not likely to pose much of a problem.

 

[AAP]

Clean it off with some fine grit sand cloth.




Probably right about being a loop to Refrigerator

You never want to run a reverse osmosis filtered water through copper tubing.
RO actually removes most all minerals from water.
Due to lack of minerals the water will attract the copper and remove molecules of copper over time .

Here is a something I found with a simple web search
Q: Why are we supposed to avoid using copper tubing for Reverse Osmosis systems?

A: The issue with reverse osmosis (RO) systems is that they reduce pH and -- because of a reduction in the buffering afforded by alkalinity -- increase corrosion (of most metal piping, including copper). The typical RO unit will remove 90 percent of salts in water, so you can assume the water salts concentration of the purified water would be about 1/10th of the content in the feed water. The aggressiveness of this purified water toward the materials into which it comes into contact is a function of its purity -- the higher the purity, the more its aggressiveness. All RO systems reduce pH (usually by 1 to 2 units).

One thought is to add a calcite filter (calcite is calcium carbonate and it elevates pH by gradually dissolving) to raise pH after the RO unit. Although in some respects, adding salt back to the water after going to all that trouble to take the salt out seems a little crazy. Can you use plastic or stainless tubing? This would eliminate the concern about corrosion. Brass tubing is significantly better than copper from the standpoint of res

 

[AAP]

I don’t have time to look at the moment. Interesting about the Reverse Osmosis filter.
I have a RODI filter for my salt water reef tank.
I have had several different Reverse Osmosis Deionization filters over the last 12 years. 75 Gallons per day 90 Gallons per day etc. I hav never had an issue with corrosion on my copper main (where I tie in my filtration) I wonder if the de ionization prevents this? Anyone? I’ll look when I can but it sounds interesting to me.

 

[Geofd]

A lot of times the cleaners under a kitchen or bathroom sink will cause this. Like comet or something. It will do this to
chrome drain piping and make it look like its going to fall apart but its not.

I work for a large college in boston we have neutralization systems for lab drain waste some of the exposed copper pipes are turning purple due to small amount of chemical smell

 

[chiraldude]

I hav never had an issue with corrosion on my copper main (where I tie in my filtration) I wonder if the de ionization prevents this?

Pretty sure you aren't running the RODI water through copper. That would be bad for fish as it would add copper ions to the otherwise pure water. Should be polyethylene tubing after the filters.
Even if the RO water was running through the copper, it wouldn't be corroding on the outside unless there are already pinholes allowing water leak out.
The comment was about what the corroded pipe was being used for. Someone suggested it was going over to a fridge for an icemaker and carrying RO water.