Or, how to find a broken coupling amidst 400 feet of pipe. Below is a photo of the repair. You can see the fittings that were used to secure a three-foot length of pipe. Inside the pipe is a coupling that has been thermally fused to form a water-tight seal.
This video shows just how messy a job this was. It took about two hours to dig and drain this one section. It took several tries over two days before they found the area where the coupling had failed.