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On Wed, 20 Aug 2003, Peter J. Thomas wrote:
> Chances are the pipe was eaten away by the concrete.  Old radiant
> heating used copper pipes buried in the slab.  Concrete is a base
> (opposite of acid) and slowly eats at copper.  Very interesting, the
> systems failed in about 40 years.
It is possible the leak is caused by a piece of steel touching the copper
piping; I've fixed several hydronic systems where the copper had been
touching a piece of rebar or tie wire, and only corroded through at that
spot.
To find a leak in a slab, I shut down the system but leave the water in
it.  I open the system and pump air into it (25-30 psi).  The resulting
air leak is much easier to locate; I use a stethascope on the floor to
pinpoint it.
Good luck
Marty Scarr
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