I've had copper half buried in regularly wet cement for decades. I chipped a bit away to find no corrosion. Lots of houses have pipes in floor concrete, but resulting leaks are very rare.
(Reply to anonymous contributor) That's a bit like saying my Auntie Elsie smoked 60 a day all her life and didn't get lung cancer, heart disease etc and therefore it's a myth that smoking is harmful. FWIW I have several times seen copper pipes buried in concrete that are corroding. It's generally accepted that this may happen and that it is bad practice to install pipework this way (illegal in the case of gas), so I've changed the text to indicate this.
--John Stumbles 11:04, 24 December 2006 (GMT)
Millions of houses have copper in concrete, but corrosion leaks are rare, smoking deaths are common. Not comparable.
The prime reason for denso et al is thermal expansion rather than corrosion. Copper carrying hot water in concrete can pull soldered joints apart or break itself as it expands and the conrete doesn't. There was a thread debating this in ukdiy recentishly.
(Reply to anonymous contributor)
Do you have a reference to the thread (at google groups)?
With regards to gas pipework; movement - due to thermal or other causes - is referred to by BS6891:
8.8.3 Pipes buried in concrete ground floors shall be protected against failure caused by movement
But the Standard also talk about corrosion:
... Reference should also be made to 9.2.1 for the application of adequate corrosion protection.
Where 9.2.1 is:
9.2 Buried pipework 9.2.1 Internal environment 188.8.131.52 Pipework that is buried in a solid floor or wall shall be factory sheathed, or protected on site by wrapping or with suitable bituminous paint protection. ... COMMENTARY AND RECOMMENDATIONS ON 184.108.40.206 Protective measures are applied as a precaution against electrolytic and/or chemical corrosion.
BS5444(1990) (on Central Heating) recommends:
Where it is necessary to run short lengths of circulation pipework in concrete floors or in walls they should: ... be adequately protected from damage and corrosion
I've certainly observed corrosion to buried pipework in practice. I'm sure thermal and other stresses on pipework buried directly in concrete, especially carrying hot water, may also cause problems. However the practical implications are surely the same: buried pipework requires adequate protection against these problems (as well as from heat loss in pipes carrying hot water, natch).
Risk factor magnitude
I guess its all a question of the magnitude of the risk factor. If millions of houses have copper direct in concrete, yet gas leaks from this are a rarity, then we could conclude that corrosion is a minor risk, one far below the level of the many other risks in houses.
This doesnt make a difference with new installs, but it does matter to whether people with existing copper in conrete would be well advised to dig it up or leave it alone and concentrate on the bigger risk factors in homes.
I googled but didnt find the thread I had in mind. NT 05:34, 2 January 2007 (GMT)