Valve tower at Upper Lliw reservoir with bridge and bridge abutment

The valve tower at Upper Lliw reservoir is a circular structure built from sandstone ashlar, featuring a leaded domed roof and designed in a classical style. The tower showcases finely cut channelled rustication and is topped with a large curved cornice moulding. It has a deep plinth with an ogee-moulded top that surrounds an arched doorway on the west side. There are three arched windows, each with moulded surrounds and stone sills. Below the plinth, there is a prominent semi-circular or bull-nose base moulding, with channelled stonework extending underwater. The dome is adorned with raised ribs and a pierced metal crown at the top.

Adjacent to the tower is a delicate footbridge that features a shallow arch made of four curved cast-iron pieces with open spandrels, where each pair meets at the center. The bridge is equipped with iron railings topped with ball finials on the posts and horizontal rails. The west end of the bridge rests on a semi-circular abutment that has a large ring moulding matching that of the tower, along with two quadrant curves of railings.