Flow isolation determines and isolates groundwater from entering sanitary sewer lines. Flow isolation is performed in sewer lines where groundwater has been determined to enter the sanitary sewer in significant quantities.
Isolation of ground water is undertaken during the early morning hours (midnight to 6am) when residential usage is at a minimum. Portable pipe weirs are placed in the targeted sewer lines to measure the flow in micro-systems of approximately 10,000 linear feet. These measurements are then correlated with the data from continuous flow monitoring, and the results determine those areas actually experiencing excessive groundwater infiltration. The gallons per day per inch-diameter-mile (idm) is calculated in order to isolate the areas contributing significant infiltration. In coastal cities and where ground water levels are high, flow isolation can be a very effective tool in locating extraneous flow.