Backhaul is a contractual transaction where natural gas is moved on a pipeline in the opposite direction of flow. For example, on a pipeline that is flowing north to south, a shipper might deliver gas into a pipeline at a southern delivery point and take receipt of the gas at a northern delivery point.
In a backhaul transaction, gas does not actually flow in the opposite direction. Pipeline operators simply provide gas to the shipper from the upstream flow, and move that much less gas down the line, until the amount of gas provided is replaced by the gas delivered by the shipper at the downstream point. Pipelines typically have rates for backhauls, which are lower than rates for forward hauls. This is because a backhaul actually saves the pipeline operating expenses since it is required to move a smaller volume of gas over the portion of the path between the receipt and delivery point.