Invert elevation is the height between a sewer pipe and a given bench mark, usually the top of the street or finished floor. Contractors doing sewer pipe installation must ensure that all sewer pipes they install meet the invert elevation height. With the right tools and direction, you can quickly calculate the invert elevation of the installed sewer pipe.
Find the benchmark the city or local building department is telling you to use, usually the top of the finished road.
Remove the manhole cover if you are calculating the invert elevation for a city sewer pipe.
Insert the tape measure into the manhole cover or hole where the sewer pipe is located. Try to put the tape measure at the top of the sewer pipe. Make sure the tape measure is in the middle of the pipe where the sewer pipe is its tallest.
Read the tape measure height against the top of the road or top of the hole. This reading is your invert elevation.