There are a variety of reasons why utilities companies test sewer systems, like checking for leaks and monitoring how many systems are tied into them, and understanding the methods for testing them can help you stay informed on what to expect during an announced inspection. The two main tests these companies perform are the smoke and hydrostatic ones, with each yielding a different data set which can be used to evaluate the health of the overall system.
During a sewer smoke test, a pump is used to push smoke into a sanitary sewer line. The smoke will flow through the system and find ways to escape above ground, such as storm drains, manhole covers and uncapped lines. The smoke can also find the surface through breaks or cracks in the system, loose pipe connections and illegal inflow points, giving utilities companies a map of the system for maintenance and construction tasks. Before utilities conduct a smoke test, relevant information is given to area residents including who to call if the smoke enters their home or office, when the test is being performed and what the company hopes to learn from it.
In a hydrostatic test, an incompressible liquid is pumped into a closed system to raise the pressure, once the pressure is at the level specified for the container, inspectors measure any shape deformations. These are performed on pipes, gas canisters and pressurized tanks as the last stage in the manufacturing process and as ongoing maintenance checks. The pumps used in this type of test can also push chlorinated water into the system for purification purposes or to test a repair before a line is reopened.
Utility companies routinely test sewer systems by using smoke or colored water. This helps pinpoint leaks or breaks in the line as well as map out system connections and discover inflow points. The companies will send out information packets to area residents detailing what is going on, when it is happening and what to do if there are problems.