Is there a piece of equipment that yo can locate the path of plumbing
and utility pipes under and in a houses foundation?

If it a metal pipe and not deeply buried, a metal detector should be
able to find it. It would also find nails and other metal too so it
might not be easy.

Ground penetrating radar is used by professionals. Unlikely to be for
hire because they require expert use but there are many surveying
companies and the like who use them for tracing buried utilities.
Won?t be cheap, but if essential you might do search for ?ground
penetrating radar? and add a few other terms like ?for hire? or
?utilities? until you find someone in your area.

Best

When I needed to trace the pipes going to my barn, I was able to rent
a locator from the same place where I rented a backhoe. Here's a link
to the company that makes these devices.   http://www.schonstedt.com/

The yellow one is pretty simple to operate. But if you possibly have a
lot of other crap buried in your lot, like I did, the orange one works
better. It has a clamp that goes on one end of the pipe and it sends
it's own frequency through the pipe to isolate it.

jay

I saw an episode of a renovation program where a plumbing/drain
specialist was using a video camera to inspect drains. The camera also
sent a signal which could be picked up by a detector. This provided
not only location of the pipe, but also accurate depth.

It might have been one of these: http://www.plumbingsupply.com/locator.html

Too expensive for an individual unless you're going into the business,
but on the program they mentioned that having them come in to
inspect/trace pipes was pretty reasonable - in the $200 range.