The Tai Tam (Bowen Road Conduit is one part of the Conduit from Tai Tam Reservoir to Albany [Filter Beds] [1887- ]. For more information about this early tap water project see here.
Shortage of water was a problem in Hong Kong since the early days. In 1860 the new governor Sir Hercules Robinson reported that "the population of Victoria had suffered very keenly during the previous winter from the scarcity of water". To overcome future shortages, a small reservoir was built at Pok Fu Lam. The winter of 1865 was dry again and plans were made to built a bigger reservoir at Pok Fu Lam. The governor Sir Richard MacDonnell decided to built this reservoir against the concerns of his advisors.
Spotted two of these. Marker is approximate.