This is Atlantic Water Garden's FilterFall - Bulkhead . We have a large selection of Filtration/FilterFall Replacement Parts and other pond supplies from Atlantic Water Gardens.

Manufacturer's Description
The Filterfalls is an up-flow filter. Water flows from the pump through the bulkhead fitting into the swirl chamber at the bottom of the filter enclosure; then through the grate and filter mat where solids are removed. Lastly, through the media bag and filter material, and out over the spillway.