South Water Tower Building in 1952
Here is a photo of this building.
As you can see there was a steel tank on the top that held a supply of fresh water for filling up the steam locomotives of British Railways. Two wells in the fields further up the track to Nethermuir had pipes laid to the tank to fill it up. The tank and the railway track alongside it were removed when steam trains were replaced by diesels in the late 1950's.