Alwen Water Scheme (nprn 85178) was constructed for the Corporation of Birkenhead between 1911 and 1921 to provide a water supply and comprises Alwen Reservoir, Dam (nprn 85182) and Filter House. Various housing is associated with the scheme: a manager's house (nprn 408482), terrace of workers? housing (nprn 85249) and barracks (nprn 85248) for the construction workers.
The Filter House, a large single storey building with rendered brick walls under a slate roof carried on steel trusses, stands below the dam. It eventually contained sixteen batteries of six Bell's Patent Filters, but is now devoid of equipment, its functions having been superceded by a new water treatment works built some 100m to the east.
B.A.Malaws, RCAHMW, 17 November 2008.