I have a length of pipe from the water meter to the house which has a leak. The problem is the pipe is 1 KM long at approx 1meter depth across two fields. The black pipe is the old alkathene 3/8 bore approx 17 mm diameter we have dug at four trenchs but not found the leak. As the pipe is in the ground we could insert a new pipe inside but the small blue 1/2" is large is there a product on the market which allows the old pipe to become a conduit for the new. If I have to dig up and relay this will cost £3,000. Any ideas.