EPAL is the successor of the centuries-old CAL- Companhia das Águas de Lisboa, the concessionaire for supplying water to the city of Lisbon from 02 April 1868 to 30 October 1974, when the concession agreement ended its term. EPAL – Empresa Pública das Águas de Lisboa was then set up. It kept this name until 1981, when it changed it to EPAL – Empresa Pública das Águas Livres.

On 21 June 1991, through Decree-Law no. 230/91, EPAL – Empresa Pública das Águas Livres was converted into a Limited Liability company with exclusively state capital, which afforded it greater flexibility regarding its management in order to carry out its strategic development and fulfil its mission. Its name then became EPAL – Empresa Portuguesa das Águas Livres, SA. In 1993 it was included in the then created group - Grupo AdP – Águas de Portugal SGPS, SA.

EPAL – Empresa Portuguesa das Águas Livres, S.A. is currently a company belonging to the state corporate sector, 100% held by AdP – Águas de Portugal, SGPS, S.A., and subject to the legal Framework inherent in this qualification, namely that set forth in Decree-Law no. 133/2013 of 03 October.

Up to 1935, EPAL’s intervention scope was limited to the supply and distribution of water in the Lisbon council. As of this year, EPAL began to provide high-level supply to the municipalities of Oeiras (1935), Cascais (1941), Azambuja (1945), Vila Franca de Xira (1946), Sintra, Loures and Odivelas (1948), Alenquer (1950), Alcanena (1955), Santarém (1958), Arruda dos Vinhos and Sobral de Monte Agraço (1964), Cartaxo (1978), Amadora (1979), Mafra (1981), Torres Vedras (1988), Entroncamento and Torres Novas, (1993), Ourém (1994), Vila Nova da Barquinha and Tomar (1995), Constância (1996), Porto de Mós, Leiria (1998), Batalha (2003) and the Águas do Oeste multi-municipal system (2003), which serves the municipalities of Alcobaça, Bombarral, Cadaval, Caldas da Rainha, Lourinhã, Óbidos, Peniche, Rio Maior and Nazaré. The municipalities of Sobral de Monte Agraço, Arruda dos Vinhos, Azambuja, Alenquer and Torres Vedras began to be supplied by Águas do Oeste. The municipalities of Entroncamento and Vila Nova da Barquinha began to be supplied by the Águas do Centro multi-municipal system (2010) and the municipality of Torres Novas began to be supplied by Águas do Ribatejo (2011).

Since July 2015, the EPAL's responsible for the delegated management of the Águas de Lisboa e Vale do Tejo (LVT) multimunicipal system supply for water and sanitation, by Decree-Law no. 94/2015 of 29 may, which includes 86 municipalities.

In 2017, the multi-municipal System of Water Supply and Sanitation system of Lisboa e Vale do Tejo, by Decree-Law no. 34/2017, 24 march, adopted the designation of multi-municipal System of Water Supply and Sanitation of the Vale do Tejo, in the sequence of the division process that gave rise to two new systems-municipal - multi-municipal system of Sanitation of Waste Water of the Great Lisboa and West, and multi-municipal System of Sanitation of Wastewater from the Setúbal Peninsula – and the two new societies – Águas do Tejo Atlântico, SA and Simarsul, SA – was awarded a concession for the exploitation and management of those 2 new systems.

The concession for the exploitation and management of the multimunicipal water supply and sanitation of the Águas do Vale do Tejo, was assigned to the Águas do Vale do Tejo ( ADVT) and the EPAL – Empresa Portuguesa das Águas Livres, S.A, its delegated management.