A casing surrounds a horizontal axis to define a cavity. The cavity has a top, a bottom, and axially front and rear ends. The casing is configured to conduct a mixture of a liquid and debris through the cavity from the front end to the rear end. Front and rear walls cap the casing at the front and rear ends. A horizontal outlet tube extends through the rear wall and defines a horizontal outlet channel with a bottom. A transversely-extending weir extends upward from the bottom of the cavity. The weir has a horizontal top edge located above the channel bottom and spaced below the top of the cavity, and further has fluid flow apertures below the channel bottom.