Naperville, Illinois, has been battling stormwater inflow and infiltration in the city’s sanitary sewer collections system for years. But after a natural calamity a couple years ago, the staff of the city’s Department of Public Utilities realized they needed to step up their game.

Bringing a new approach to the problem has made a huge difference in just two years, and officials expect to continue reaping the benefits.

That new approach includes some new techniques...