The main sources of Metro Manila’s water supply are the Angat, Ipo, and La Mesa Dams. The water from these dams are then processed by the La Mesa and Balara Treatment Plants, which converts it from a raw state to clean and potable water.

The water from the Angat Dam, the major supply source for the metropolis, is funneled directly to Ipo Dam. It then flows a distance of 6.4 kilometers to Bicti, after which it passes through five aqueducts—each about 16 kilometers long—to the La Mesa Dam and the La Mesa Portal. From the La Mesa Portal, 60% of the flow goes to the nearby La Mesa Treatment Plant, out of which another 40% again travels a distance of 6.8 kilometers to the Balara Treatment Plant.  The La Mesa Water Treatment Plant, with very minimal electromechanical equipment, relies mostly on water’s hydraulic properties to backwash its filter and gravity to convey raw water from the source into the plant and out into the distribution system.

It can only process 2,400 MLD (million liters per day) of raw water, while the Balara Treatment Plant, which has a full production capacity of 1,600 MLD, can supply more than 6 million people throughout the metropolis.

When both Balara and La Mesa Treatment Plants are operation, the total processing capacity will be 4,000 mld. The La Mesa Water Treatment Plant serves the western half of Metro Manila, while the existing Balara Water Treatment Plant supplies the eastern half.