A break in the pipe would result in a major leak, and possibly a fire or explosion. It was an old, 3-inch pipe. As I approached the house, I saw that the newer part of the pipe, where it passed through the front wall, was the 4-inch size. It doesn't take rocket science to figure out that connecting a large drain to a smaller one below will create full employment for Roto-Rooter. When I reached the house itself, I saw that the front retaining wall was crooked, leaning, and contained wood left from the concrete forms.
Wood embedded in concrete is a great pathway for termites to enter a house.
The wall was fairly new, all right, but it definitely had not been installed by a professional. Whoever installed it didn't even bother to get it level, and there were no bolts to connect the walls to the concrete. In a strong quake, the house could slide down the hill if it is not properly anchored. Parts of the roof framing were badly damaged by decay. There were gaps in the exterior that would let water into the walls.