"Walter R." wrote in message
...
Good idea, but what about plastic drainage pipes, including the main
drain?

Any ideas welcome

--
Walter
www.rationality.net

A thermal imaging camera might be the answer, but I'm not sure if it can
"see" through 6" of concrete. Local heating/air conditioning contractors
may know where to get one. If not that, try the local fire dept. The more
affluent dept's (they are quite expensive) have them to see people through
smoke. Maybe they can call a trip to your house a "training exercise" to
use it. :-)