The inspection and repair of plumbing systems is necessary to find and repair small leaks before they become large disasters, but how do municipalities test their sewer systems on such a large scale? These systems feed into hundreds or thousands of homes, commercial buildings and government properties and can even be tapped into illegally by property owners. Municipal utilities companies usually hire plumbing inspectors to perform hydrostatic and smoke tests to accurately map out the access points to the system, find leaks or blockages and plan maintenance schedules.
During this type of test, an inspection crew will isolate a section of the system to pressurize and then measure any deformations in the pipes or pump colored water into the system to better identify leaks. A hydrostatic test pump is used to fill a pipe or pressurized container with uncompressible liquids, like oil or water, when a dyed liquid is used, leaks can be easily seen. This is usually done on individual buildings or on sections of pipe before they are put into place, and the pumps can also be used to push chlorinated water into a system for purification.
Tests using smoke are more common for large systems as the smoke will flow along the pipes and be visible at leaks, broken manholes and sources of inflow. Knowing which lines are connected and which are independent is an important factor in construction, city planning and maintenance schedules. This testing can help a municipality update system maps, pinpoint leaks and even find illegal sources of inflow such as uncapped lines and unauthorized roof drains to better plan future projects and budgets.
Routine testing of a municipal sewer system is done with a variety of methods, such as hydrostatic and smoke tests, to create a more complete data set. This testing can map out a system’s branches, identify leaks and even provide information on illegal or unknown sources of inflow. Utilities companies usually perform these tests, with their own crew or a hired specialist, and inform residents in the area prior to testing.