Council water services manager Quentin Adams reassured residents not to be alarmed about smoke coming from their household drainage or the ground outside properties during the testing.
"If you see smoke during this period and think that it is caused by an actual fire or see flames, please follow normal emergency procedures."
The council has been completing routine, non-toxic smoke testing of wastewater pipes in streets around Alexandra this week and will begin testing in Cromwell next week.
Smoke testing involves pumping smoke into the wastewater network to identify any cracks, breaks or faulty connections.
Mr Adams said the testing and any maintenance repair work required was important to stop the wastewater system being overloaded during heavy rainstorms.
Residents will receive a letter from the council advising them when testing will begin in their area.
