I don't get the bike out for walks of less than fifteen minutes, and this water tower is ten minutes away... but the photo is taken from the castle and priory, about five minutes away...
Obviously the water tower is the red brick structure on the left, topped with its cast iron tank.
from a PDF about Lancaster's canalside mills...
Moor Lane South Mill (Between Bridges 101 and 102) This started as a sailcloth factory and, after being bought in 1825 by Samuel Greg (of Quarry Bank Mill in Cheshire), it was converted to spinning and weaving cotton. The current building dates from 1825–31. The Storeys took it over in 1861. After the mill closed in 1982 the site became offices for Reebok, who then moved out, and it is now NHS offices. The red water-tower is a local landmark.
The is another at a former mill in Caton a few miles up the river. Next time I'm out that way i'll try to bag a photo... and apparently another just on the other side of that hill with the memorial on top.
edit... who said there's no water towers in the hillier areas?