A valve tower on the main dam of the Grwyne Fawr reservoir, completed in 1928. The valve tower was built up from the base of the reservoir as the dam wall was built and finished with the same carefully dressed stone.
Source: Rev DA Tipper in his 1975 book "Stones and Steam in the Black Mountains
The square valve tower has a door in its southeast wall accessed from the top of the dam. There was a plaque in the semicircular area above the door which reads
?Abertillery District Water Board
Grwyne Fawr
Reservoir
Height above Sea Level 1790 Feet
Height above dam 156 Feet
Inaugurated 28th March 1928
By Councillor David Lewis J.P.?

J.J.Hall, Trysor, 5 February 2008