A five-year building boom, laid pipe fast
Chandler's population more than doubled within five years after its coal mines closed by the mid-1940s, with houses built rapidly ahead of the town's 1953 incorporation. Plumbing installed at that pace, across that many homes in that short a window, tends to age out in a fairly narrow band of years -- meaning a lot of Chandler homes are approaching supply-line and drain-line service life at roughly the same time.
Why so many Chandler homes need similar plumbing work
Because so much of Chandler's housing stock was built within the same five-year postwar window, water heater installation, drain and sewer service, and supply-line upgrades tend to come due in clusters rather than being spread evenly across decades the way an older, more gradually built town's needs are.