Thirlmere Aqueduct Construction Facts

The Thirlmere Aqueduct was constructed by the Manchester Corporation Water Works to carry approximately 250 Ml/d from Thirlmere Reservoir to Manchester. The construction of the reservoir and aqueduct was authorised by the Manchester Waterworks Act of Parliament. The first phase was completed in 1897 and, for the pipeline sections, subsequent phases were completed in 1925.
The aqueduct is 95 miles 1642 yards long. Its most common form of construction is in cut and cover which consists of a concrete covered channel 2.16m wide and 2.16m or 2.39m high of "D" section. There are 3 3/4 miles of cut and cover section comprising approximately 300mm thick concrete horseshoe section. Typically, the conduit has one metre cover and traverses the contours of hillsides.


Where this was not practical, tunnel construction was used, generally of similar concrete section. Lengths of rock section to the North of Kendal were left with unlined walls and roof but with a concrete floor. There are 14 1/8 miles of tunnel section.
Where the aqueduct route had to cross river valleys multiple pipelines were used. The pipelines connected into the conduit sections by chambers referred to as North Wells (where the conduit changed into pipeline) and South Wells (where the pipelines re-entered the conduit). The first line was completed in 1897, Line 2 in 1904, Line 3 in 1914 and Line 4 in 1925. The first three pipelines were constructed of cast iron and the fourth line consists of steel pipes with lead joints. There are 33 miles of multiple pipe siphons.


Pipe Thickness - 1 7/8" , ( 47mm ) see picture

The aqueduct has a nominal capacity of 220 Ml/d from Thirlmere to Kendal. From Kendal to Manchester the capacity is approximately 255 Ml/d. Up to 200 Ml/d can be injected into the Thirlmere aqueduct at Kendal via the Thorneybank pipeline from the Watchgate WTW. At Hoghton service reservoir near Preston up to l00 Ml/d can be transferred into the aqueduct and 95 Ml/d transferred from the aqueduct to the Lancashire Conjunctive Use System.
It takes approximately thirty hours for water travelling from Thirlmere to arrive at Manchester