Radyr weir, Cardiff

This weir was built in 1774-75 to supply water from the river Taff to Melingriffith tinplate works. The mill feeder survives, and you can walk its entire length on the adjacent footpath (north of Forest Farm Country Park).

Photo of Radyr weir and steam train c.1920The old photo of the weir, with a train on the Taff Vale Railway’s main line, dates from c.1920 and is shown here courtesy of Cardiff Libraries. The house near the centre was beside the sluice at the feeder entrance.

Parts of the sluice still exist. It controlled how much water entered the feeder. A nearby overflow returned any surplus water from the feeder to the river along a culvert, which passes under the cycling and walking route south of the weir. That route was originally occupied by a tramway which transported metal sheets from Pentyrch ironworks to the tinplate works.

There was a weir here before the current one, possibly even in medieval times. The tinplate works evolved from a forge, which itself had probably replaced a corn mill – all supplied from Radyr weir. To see photos of the works, click here for our page about the Melingriffith pump (which supplied the Glamorganshire Canal with water raised from the works’ outflow).

The 1948 aerial photo, courtesy of the Welsh Government, shows the weir in the top left corner and the feeder flowing past open fields to the tinplate works, bottom right.

Aerial photo of Radyr weir and Melingriffith feeder in 1941The weir sometimes halted corpses floating downriver, including the body of Ralph Boyle, aged 4, who fell in near Pontypridd in 1896; and of colliery pumpsman Thomas Lewis, 52, who fell into the river Cynon near Mountain Ash in 1914. In 1883 Rev Lewis Price, vicar of Llandeilo, Carmarthenshire, lost his son Hilary, 17, in a bathing accident at Radyr weir. Hundreds attended Hilary’s funeral in Llandeilo.

In 2016 the river’s power was harnessed again in a Cardiff Council initiative. A channel diverts water to two Archimedes screw turbines, which can generate up to 394kW of electricity at any one time. In partnership with Natural Resources Wales, a fish pass was also installed to help salmon and other fish move upriver to spawn.

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