Thread: Copper corroding at passage through slab

Other copper was fine, the only significant corrosion was at this water line coming up through the concrete basement floor slab below the tile.

1) Is this likely all or mostly chemical corrosion?

2) Is there a practical fix other than breaking out the slab, replacing the corroded copper, and properly sleeving?

3) How do you properly sleeve copper pipe in locations such as basement floor slabs were you are concerned about water intrusion?


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Is that the water main or an oil line? Both are protected in rubber sleaves nowadays. No one runs oil in the slab anymore and that should be changed out if it is oil. If it's water main nothing to do but wait and hope and of course mention the corrosion in your report.
Copper corrosion from contact with concrete.

Originally Posted by Michael Thomas

1) Is this likely all or mostly chemical corrosion?

Looks like it.

2) Is there a practical fix other than breaking out the slab, replacing the corroded copper, and properly sleeving?

That is the "practical" fix. Anything else and you are not really "fixing" anything.

3) How do you properly sleeve copper pipe in locations such as basement floor slabs were you are concerned about water intrusion?

Carefully.

The reason for the sleeve is several fold: keep the items isolated from each other; allow for expansion/contraction; eliminate physical damage by contact with each other.

The sleeve could be slipped over the copper, tied and sealed around the pipe below the slab, then the annular space around the pipe within the sleeve sealed with sealant above the slab.

Hummm... just found this:

http://www.copper.org/applications/p...t_concrete.pdf

And this:

"According to the Portland Cement Association the interaction of copper with both dry and wet concrete should not cause a corrosion concern. However, copper should be protected when it comes in contact with concrete mixtures that contain components high in sulfur, such as cinders and fly-ash, which can create an acid that is highly corrosive to most metals including copper..."

Copper.org: Plumbing: TechCorner - Is There A Problem With Embedding Copper Tube In Concrete?

This is in the IRC. (underlining and bold are mine)
- P2603.3 Breakage and corrosion. Pipes passing through or under walls shall be protected from breakage. Pipes passing through concrete or cinder walls and floors, cold-formed steel framing or other corrosive material shall be protected against external corrosion by a protective sheathing or wrapping or other means that will withstand any reaction from lime and acid of concrete, cinder or other corrosive material. Sheathing or wrapping shall allow for expansion and contraction of piping to prevent any rubbing action. Minimum wall thickness of material shall be 0.025 inch (0.64 mm).
- P2603.4 Sleeves. Annular spaces between sleeves and pipes shall be filled or tightly caulked as approved by the building official. Annular spaces between sleeves and pipes in fire-rated assemblies shall be filled or tightly caulked in accordance with the building portion of this code.

Thanks.

If that was my place, I'd clean it up and paint it. And I'd set some mouse traps.