Stone and timber framed masonry weir across the river Taff. Water was abstracted on the west side of the river into the feeder leat (nprn 91500) which crossed the Taff by an aqueduct (nprn 91501) and provided water for the Glamorganshire Canal (nprn 34425) at Abercynon. From map evidence (Ordnance Survey 25in map first edition of 1877) it appears that the overflow from the pond supplying Mafon Flannel Mill (nprn 419552) discharged into the river on the eastern bank immediately above the weir.
Site visited B.A.Malaws, December 1978.