Full Report for Listed Buildings

Summary Description of a Listed Buildings

Reference Number
Building Number
Date of Designation
Date of Amendment
Name of Property
Lake Vyrnwy Straining Tower and approach bridge  


Unitary Authority
Lake Vyrnwy Dam  
Street Side
On the north-east side of Lake Vrynwy visible from the dam; approached by a gated bridge from the lake-side road.  


Broad Class
Water Supply and Drainage  

The Straining Tower was built between 1881 and 1892 to the designs of George Frederick Deacon as part of the heroic Vrynwy Dam project to supply water to Liverpool via an aqueduct 110km long. The tower stands in the lake to extract and strain the water at the beginning of the pipeline. This was the first of several long-distance water supply schemes in Britain which were vital to urban development in the late-Victorian period. The reservoir created was the largest in Europe at the time of its completion. The whole scheme was designed by the engineers George Frederick Deacon and Thomas Hawksley, although the Straining Tower was the work of Deacon. Water was first supplied to Liverpool in 1892.  

A romantic tower said to have been modelled on the medieval castle of Chillon, Lake Geneva, but more reminiscent of the contemporary work of the architect William Burges. The tower is 52m high of which about 35m normally appears above water level. Constructed of mass concrete with snecked faced local rubble and utilising an early prototype form of reinforced concrete at gallery level, consisting of continuous steel wire wound mechanically onto cast-iron chairs within the wall. Circular tower with machicolated parapet and pierced balustrade to the wall-walk; above that it is octagonal with 2-light openings to alternate faces and is crowned by a swept pyramidal roof including gabled small-pane dormers. On the south-east side, corbelled out from the main tower above water-level, is the circular stair-tower with cross-frame windowed bellcote and steep conical roof. Both roofs in copper sheeting on a timber frame, said to be of Indian oak; roofs and gables decorated with weathervanes and finials. Below the parapet the engine room is lit by shouldered lancets, and two-light medievalist windows light the washing floor where the tower is entered; square-headed doorcase with small-pane overlight. The tower is connected to the shore by a stone bridge of 4-segmental arches; parapets with dressed coping. At the shore end steps lead up to road level with massive gate-piers and a pair of wrought iron gates.  

The base of the tower, below water level, contains space for three strainers, each nearly 8m high, together with adjustable inlet pipes which can be raised or lowered externally to ensure the intake of clear water from near the surface of the lake. The tower is entered above this at washing-floor level to which the strainers are raised for cleaning by sprays within iron casings. There is an inspection platform below this level from which trays are raised to catch cleaning water. Spiral staircase rises to engine room which retains its complete original equipment. At the centre of the room is a two-cylinder hydraulic engine by Glenfield Co. Kilmarnock, 1889, which is powered from a reservoir on an adjacent hill providing a 35m head. It operates three large hydraulic rams to lift the strainers and two further rams to raise and lower the inlet pipes. The domed roof of the engine room is of shuttered concrete with wrought iron ribs and has a central lantern, formerly open to a railed gallery. The hydraulic rams pass through the dome to the floor above. On this floor is an octagonal room leading onto a wall-walk giving access to the winches for the inlet pipes, contained beneath a gabled hood; the bellcote is also at this level. A cantilevered timber staircase rises to the loft where the roof structure is supported on a cross-frame base with pendant.  

Reason for designation
Listed Grade I for its national importance as an outstanding achievement of Victorian water engineering, its exceptional completeness in structure and equipment, and its picturesque qualities. Group value with Lake Vyrnwy Dam.  

Cadw : Full Report for Listed Buildings [ Records 1 of 1 ]