Determine where the sewer line is leaking. It’s usually the spot that is oozing to the surface.
2) Insert an air hose inside the line past the point of the break and apply air pressure to empty the line of remaining water.
3) Find a water line hose one size smaller than the sewer water line. Insert it into the larger pipe and push it in, well past where the break is thought to be.
4) Keep pushing it into the pipe until the far end is submerged in water. You can tell by blowing into the smaller pipe and hearing bubbling.
5) In the space between the two pipes, inject an expanding urethane foam crack filler. The harder, less expanding type works best.
6) Hopefully, the urethane ran down to the water level, began to foam back up, sealed the crack, and you will see it oozing back out the top.
7) Clean up the excess foam, and wait for it to harden.
8) Connect the inner, smaller water line to the system and apply water pressure again.
This method will not work unless the sewer line slopes downwards and away from you. You need the far end of the smaller, inner pipe to be submerged in water to prevent the foam from sealing the far end shut.
Vertical water lines work the best. Horizontal lines do not.
Attaching a long, narrow tube to the urethane foam applicator helps to inject the foam more easily into the gap between the inner and outer pipes.