Under the bathroom floorboards - copper pipes with blue corrosion

[bmouthboyo]

So I just removed a non load bearing wall between my toilet and shower room in my 70's bungalow.

Looking to reroute some of the pipes to relocate the sink and when looking under the floorboards I noticed that the pipes run around the perimeter of the room and when passing the soil pipe area the builders seem to have simply dumped all sorts over them. Bricks, morter, wood etc. I noticed a lot of blue powder so tried to expose the pipes a bit and noticed they are covered in it.

I assume this is the coper corroding? Is it a case of cleaning them up and seeing condition of is this normal?

 

[Mr Chibs]

Yes, looks like copper. You shouldn't have copper pipe touching mortar/cement, as over time it can rot it.
Should be insulated or wrapping in Denso Tape (think that's what it's called)

I'm no plumber but some will be along to tell you what's what.

 

[denso13]

Don't know if you have anything leaking from above, looks like mess you get when someone doesn't aim straight. Normal cement won't affect copper.

 

[JohnD]

The soil pipe may also been leaking. Mortar is often smudged round clay drains in a futile attempt to repair them.

Clay is inclined to crack.

 

[kidgreen61]

As said above, that copper is corroding because it hasn't been protected from mortar etc.
I would renew it.

 

[Madrab]

Lime based mortar/cements and copper don't mix, the lime will quite happily eat copper. Most mortars/cements, apart from 1 type (External grade portland) contain at least some lime.

If that is standard internal mortar/cement and quite old then chances are it will contain lime to some degree.

 

[JohnD]

It also depends on the water content. Where I live, clean water leaves green stain. Blue corrosion indicates the presence of sulphur (e.g. sewage or plaster)

 

[denso13]

Lime based mortar/cements and copper don't mix, the lime will quite happily eat copper

It's sulphur which causes problems. Screened/crushed limestone can be used as a backfill to protect copper against corrosion.

There is nothing in normal portland cement which will eat copper at all.

 

[Madrab]

There is nothing in normal portland cement which will eat copper at all.

Your right but most cements/mortar that are used in the UK aren't purely portland cement, most are a mix of portland and lime. I also believe a lot of plasters, especially older plasters had a high lime content

It is well known that lime eats copper

Types Of Mortar And Their Applications | Guides | Precon Products

Mortar is the element that bonds bricks and other masonry units together, providing structural capacity and adhesive to bind and fill gaps between brick, concrete or stonework.

www.preconproducts.co.uk

 

[denso13]

Your right but most cements/mortar that are used in the UK aren't purely portland cement, most are a mix of portland and lime. I also believe a lot of plasters, especially older plasters had a high lime content

It is well known that lime eats copper

Types Of Mortar And Their Applications | Guides | Precon Products

Mortar is the element that bonds bricks and other masonry units together, providing structural capacity and adhesive to bind and fill gaps between brick, concrete or stonework.

www.preconproducts.co.uk

That link is for specific manufacturer not run of the mill use.

Portland cement does not contain lime and most mortar mixes for general use are only cement/sand, no lime.

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

It is completely acceptable to bury/embed both hard drawn and annealed copper water tube in concrete. Decades of satisfactory service experience with the use of copper tube for in-floor radiant heating systems, water distribution systems and snow melting systems attest to the compatibility of...

copper.org

"A screened soil/pulverized limestone mixture is recommended as a selective backfill for copper tube to help eliminate corrosion concerns."

 

[Madrab]

That link is for specific manufacturer not run of the mill use.

Portland cement does not contain lime and most mortar mixes for general use are only cement/sand, no lime.

Have to disagree - Here is a perfect example of a general 'run of the mill' use mortar available in all the big sheds, check out it's technical spec, cement (portland)/lime/sand etc

https://tarmac-bluecircle.co.uk/wp-content/uploads/2020/02/Quality-Assured-Mortar-approved-05-09-2018.pdf

As far as lime and copper is concerned then I believe it a chemical process that lime (not limestone) and it's components can corrode copper, especially if damp until it has a coating (scale), that then shields the copper from further corrosion, like any corrosion will.

edited for bad grammer

 

[denso13]

How much lime will cause harm? Sulphur and chlorides are the worst.

Non-ferrous metals in concrete

Concrete Information Wiki

www.concrete.org.uk

"Copper is generally immune from attack by caustic alkalis and not affected by contact with lime or calcium hydroxide."

 

[Madrab]

Does limescale not corrode copper? i.e. Lime in the presence of water?

 

[denso13]

Does limescale not corrode copper?

Limescale, land contaminated with lime, lime plasticiser, all different things really. Mortar sets hard and any plasticiser sets with it. Once hard it isn't going anywhere.