Abstract: An improved hydrant diffuser, comprising a housing or box with one open end, slows and directs the flow of water from a hydrant when the hydrant has been opened to flush a water line. The diffuser can be mounted on any work truck or other vehicle having a class 3 trailer hitch receiver. A hose may be coupled to a fire hydrant to carry water to the diffuser. The other end of the hose is non-releasably attached to a 90-degree elbow which can be coupled to a flange bolted to the top of the diffuser box. The diffuser mounting to the truck includes means that allow the box outlet to be pointed straight back from the truck or in selected positions up to 90 degrees either to the right or left. A debris screen across the outlet end stops any rocks or other solid objects in the water stream.