The Laboratories and Water Quality Control Department (LAB) is EPAL's responsible body for designing, implementing, and managing the Water Quality Control Plan in EPAL's Supply System and AdVT, hence applying the principle that responsibility for a product's quality control should be independent from the water supply system production and operations.

EPAL's laboratories - located in Lisbon (Central Laboratory) - and the Water Treatment Plant of Vale da Pedra have their remote origin in the Laboratory of 100-year-old Companhia das Águas de Lisboa (CAL), which was founded in the 1930s in order to determine the 'quality of taken, disinfected, and distributed water' using the available means of the time.

The Planning, Sampling and Data Processing Department ensures the provision of sampling services and water quality monitoring for human consumption, processed water, and natural water.

LAB depends directly on the Board of Directors, where its organisational structure is that indicated in the following organisation chart.