Part of the Elan Aqueduct (nprn 95469), itself part of the Elan Valley Water Scheme (nprn 96459), the Clywedog Syphon, some 1.73km long, carries the pipeline over the Clywedog Brook. It consists of the Syphon Inlet (nprn 309622), a Washout Chamber (nprn 309623), an Air Valve Chamber (nprn 309624), the aqueduct over the Clywedog (nprn 309625) and adjacent Washout Chamber (nprn 309626) and the syphon outlet (nprn 309628).
B.A.Malaws, 08 December 2003.