Upon the implementation I 1977 of the Taipei Area Water Supply Expansion Plan, Phase Ⅲ, the original slow filter was rebuilt into the modern rapid filter with a new name, the Kungkuan Purification Plant. Years later, however, worsening pollution of water sources forced the raw water intake to relocate from downstream of Xindian Creek to the Qingtan Dam upstream. Natural, gravitational forces carry raw water taken in there through tunnels and channels to the diversion chamber in the Changxing Purification Plant. From the diversion chamber, two 1,400 mm concrete pipes and one 2,000 mm cast-in-place reinforcement concrete pipe deliver the water to the Kungkuan Purification Plant for treatment.
With a design production capacity of 480,000 ton per day, the Gongguan Purification Plant treats 520,000 ton of raw water daily. Decent potable water after a long, complete treatment process is then delivered by heavy-duty booster pumps to distribution piping system to serve daily needs of end users in the Taipei area.