Green copper pipes

[Deleted member 216148]

Hello,

We've got some flooring up in places at the moment before putting new laminate down, and I've seen some very green copper central heating pipework in the sub floor.

It's green where it goes through the wall into the next room. The sub-floor used to be full of condensation before we sorted air-bricks out a few years ago, so I'm assuming that's the cause, but it interests me that it's only really happening where it goes through the wall into the next room.

The pipe is bone dry and I've tested for leaks by placing newspaper underneath and it's fine.

How much of a problem is this? I realise that it is not ideal, but considering it's probably been like this a very long time, should I be immediately concerned?

Thank you!

 

[ReJect]

I wouldn’t be too happy about that. A chemical reaction takes place on copper if it touches damp brick or mortar.
If leaving it as is, I would insulate and also sleeve the insulation where pipes go through walls using dpc membrane or similar.
On a new install the pipes are best sleeved with large plastic pipes, much bigger diameter than insulated pipes.
Or have the pipes replaced

 

[EddieM]

if it's green its copper carbonate, inert. No worries, apart from the fact they're probably been eaten away from the inside (due to age)

 

[Deleted member 216148]

Thanks both for your replies.

It's not touching the walls, you can see foam insulation poking through from the other room, but it probably was for a long time because that foam insulation looks to be newer.

If the copper carbonate is inert, do you mean now that it's formed it isn't going to get worse? What will cause it to be eaten from the inside?

To replace, we'll have to pull up the chipboard living room floor (other side of the wall) which isn't a happy thought...

 

[JohnD]

You can clean off the deposits with a damp green plastic pan scourer, wipe off with clean rag, put the lagging back. Have a look next year and see if it is still corroding.

 

[ReJect]

The green is similar to slight rust you get on a piece of iron.
But it is serious if it is more than just a dust layer of green.
The pipes hopefully will be in good order inside especially if heating pipes.

 

[EddieM]

The green is similar to slight rust you get on a piece of iron.
But it is serious if it is more than just a dust layer of green.
The pipes hopefully will be in good order inside especially if heating pipes.

Not at all rust is iron oxide, green copper is copper carbonate its going nowhere, don't clean it off, its fine.

 

[ReJect]

Not at all rust is iron oxide, green copper is copper carbonate its going nowhere, don't clean it off, its fine.

I know the green forms a barrier, but you never know condition of pipe until you clean it off.
If left unfixed a green corroded pipe from a rad valve can pin hole due to the leak obviously

 

[EddieM]

I know the green forms a barrier, but you never know condition of pipe until you clean it off.
If left unfixed a green corroded pipe from a rad valve can pin hole due to the leak obviously

Copper carbonate once formed will not further corrode a pipe. in fact it protects it from further corrosion.

 

[ReJect]

Copper carbonate once formed will not further corrode a pipe. in fact it protects it from further corrosion.

I am not a chemical expert and just a plumber, but some chemical reactions on copper pipes will cause the green colour and can corrode the pipe through eventually if the pipe remains in contact with the chemical - like through a damp or mildly damp wall. I don’t see that often though.
Green to me proves corrosion, except where pipes would be understandably exposed to damp air or rain

 

[Deleted member 216148]

Thanks again for your help everyone, I've learnt a lot about copper tonight!

I'm tempted to take the suggestions of adding foam insulation, and slipping some DPM in the wall. I'll have to rip up the living room floor to replace the pipe on both sides, so I may as well wait for a leak then rip it up... or it might never leak if I'm lucky!

If the green corrosion really is protective I won't try and clean it.

 

[JohnD]

The reason I clean it off is so I can see if the problem still exists. Generally it doesn't and the cause was usually flux traces or maybe a weep.

I think it can also result from gritty builders dust lying on the pipe, lagging will keep it clean.

I don't see that cleaning it off will do any harm, and it may alert me to a problem.

 

[Deleted member 216148]

Hi John, ah I see your logic, I might clean a very small area then.

 

[dilalio]

Most likely that the green has formed where it has due to damp/moist air under the floor in one room different to that under the other room... The point at which these two atmospheres meet is the aperture in the wall.
Add in the surface temperature of the pipes, which differs between heating on/off and you have all the ingredients for a "dew point" to form... Condensation on the pipes with a draught across them and you have copper, water and oxygen... Which goes green