Privatising the water market in Metro Manila improved the efficiency of water services to households, but insufficient supply and tariff increases may limit these gains. This study investigates investment policy dynamics through household investment, as concessionaires pass on the cost of future capital investment to households. Using an Almost Ideal Demand System, the study estimates household water demand elasticities in Metro Manila. Water demand is elastic, mainly due to the Increasing Block Tariff structure and households having access to alternative water sources. Additional findings suggest there is still a problem in attaining efficiency and equity for water pricing structures.