"Michael Gray" wrote in message
...
On Fri, 16 Sep 2005 11:37:48 +0100, "N Cook"
wrote:

By excavating pits and freezing the pipe I localised down to a 20 foot
run
and then a 10 foot run. I've now dug 2 more pits so about 3 foot
apart in that 10 foot. 3 gallons of water an hour is just disappearing
with no trace emerging along pipe or into holes.


While I wait for more water to freeze in the freezer to
localise a bit more, anyone any ideas for electronically/
audibly trying to localise the leak. A listening stick made from a steel
rod and a wooden drawer knob certainly works against anywhere
on the pipe (thats the problem ,anywhere ,
and much same level) but nothing through the soil

Have you considered using smoke to test for leaks?
http://www.hurcotech.com/

I did consider digging out an air pump , turning off the supply at the
pavement
and blowing air back into the piping to see if it would whistle where the
leak is.