When buying used culvert pipes, make sure that the pipes correspond to the intended sizing and installation requirements. Determine the correct sizing before looking for used culvert pipes, taking steam flow dynamics and seasonal changes into consideration.
Annual fluctuations in the flow of water through a culvert pipe installed, for example, in conjunction with an earth bridge to siphon water beneath a roadway, can erode exposed soil and cause the entire structure to fail. To mitigate this risk, choose a culvert pipe of a size rated to handle annual peak flow.
One of the best ways to determine the correct size of a culvert pipe for an installation project is to take field measurements of a stream's cross section at its lowest point in the season. Find a used culvert pipe with a cross section of at least 1.25 times the cross section area of the stream. If the area is prone to floods, multiply the stream area by either 1.75 or 3.
To determine the correct culvert pipe length for a project, add the width of the roadbed with the width of both side slopes plus an extension of 1 foot on each side of the pipe. Be aware that a culvert pipe not set at a 90-degree angle will need to be of a greater length to compensate.