What the south end was actually built on
South Pickering went up in waves.
Bay Ridges came first in the early 1960s, then West Shore, and the pattern repeated north and west through Amberlea, Liverpool and Brock Ridge from the 1970s onward. Older than any of it are the village pockets. Dunbarton dates to the mid-1800s, and the streets off Rosebank Road, Fairport Road and Woodview Avenue were built between 1900 and 1940, some of them summer places that were later winterized without much thought for the plumbing.
In practice that means copper of several different vintages, cast iron stacks at the old end, and clay laterals that have had five or six decades to collect roots at every joint.