No. A stilling well is not needed. The orifice line is normally installed inside a two-inch conduit and secured in place, so there is no movement in the orifice line. It is best to install the outlet just above the sediment in the water to be measured. When the orifice line is securely installed, the unit makes accurate measurements of the water—even if the water has some movement, such as in a river. The measurement averaging time can also be increased to reduce the noise in the data, providing the same function that the stilling well does to average out the fluctuations of the water.