General Regulation for Drainage Systems: Understand Its Application and Importance in Building Construction

When discussing construction or building infrastructure, one crucial element for public health and comfort is often overlooked: the wastewater drainage system. The General Regulation for Drainage Systems is a fundamental framework governing the design, execution, and maintenance of sewage networks in Portugal, ensuring the safe and efficient evacuation of wastewater.

"Sewer pipes must ensure, under all circumstances, proper evacuation of received waste, remain accessible and easily inspectable, without impairing the building’s exterior appearance."

What Is the General Regulation for Drainage Systems?

The General Regulation for Drainage Systems forms part of the General Urban Buildings Regulation (RGEU), approved by Decree-Law No. 38 382 of 7 August 1951, and subsequent amendments. It defines the technical standards and legal requirements applicable to drainage systems in buildings and urban environments.

Its primary purpose is to ensure that all buildings have adequate sewage systems to protect public health, sanitation, and the environment by preventing contamination, infiltration, and harmful emissions.

Scope of Application

The regulation applies to:

• All new constructions – sewage systems must comply with standards from the design stage.

• Reconstruction, extension, and alteration works – existing systems must be evaluated and updated as necessary.

• Residential, commercial, industrial, and collective-use buildings – ensuring minimum sanitary conditions across all uses.

• Mandatory connection to the public sewage network – all buildings must connect via private service lines whenever a public network is available.

Historical Context

Before the 1951 RGEU, the 1903 Urban Sanitation Regulation applied basic drainage and hygiene rules. With advancing building techniques, urban growth, and increased awareness of public health, a more comprehensive and demanding regulation became essential. The adoption of the RGEU marked a turning point, introducing technical standards for:

• Design and installation of sewage systems

• Approved materials

• Ventilation and inspection

• Protection against leaks and harmful emissions

Successive amendments have modernised the regulation while maintaining its essential aim: safeguarding public health and acceptable living conditions.

Main Provisions

1. Design and layout - Sewer systems must be designed for efficient evacuation, remaining accessible for inspection without compromising the building’s appearance.

2. Piping materials - Common clay pipes, even glazed, are prohibited. Only durable, corrosion-resistant materials such as vitrified stoneware or equivalents with smooth internal surfaces are permitted.

3. Ventilation and sealing - Each drainage outlet must connect through an accessible siphon providing permanent hydraulic sealing. Wastewater pipes must vent at least 50 cm above the roof, with a main ventilation pipe mandatory for multi-storey buildings.

4. Separation of rainwater and wastewater - Rainwater drainage must be rapid and independent. Rainwater downpipes must be separate from those for wastewater discharge.

5. Connection to the public network - All buildings must connect to the public network through private service lines with adequate diameters and gradients, generally between 2% and 4%.

6. Effluent treatment in areas without public network - Where no public sewer exists, wastewater must be directed to treatment systems ensuring adequate purification. The use of soak pits or systems likely to contaminate the subsoil is strictly prohibited.

Qualified Professionals

Design, execution, and supervision of drainage systems must involve certified professionals:

• Design engineers – registered civil engineers responsible for sewage network design and compliance statements.

• Site directors and supervisors – overseeing project execution and legal conformity.

• Contractors and builders – certified by the Institute for Construction and Real Estate (InCI, I.P.).

• Municipal councils and inspection bodies – authorised to licence, inspect, and demand corrections when sanitary or structural issues arise.

Responsibilities and Penalties

Non-compliance may result in:

• Fines and penalties for owners, designers, directors, or contractors.

• Orders for rectification or demolition issued by municipal authorities in cases of health hazard.

• Civil or criminal liability in cases of false declarations or third-party damage.

Summary

Aspect	Description
Definition	Technical standards for design, execution, and maintenance of drainage systems
Scope	New buildings, reconstructions, or modifications in all sectors
Historical context	From the 1903 Sanitation Regulation to the 1951 RGEU
Approved materials	Vitrified stoneware or corrosion-resistant smooth-surface pipes
Prohibited materials	Common clay pipes, even glazed
Mandatory connection	Connection to the public sewer network wherever available
Qualified professionals	Engineers, certified contractors, site supervisors
Oversight	Municipal councils and inspection entities
Responsibility	Shared among designers, contractors, and owners
Sanctions	Fines, rectification orders, demolition, or legal liability

Practical Advice

• Always consult a qualified civil engineer before modifying or installing a sewage system.

• Ensure your property is connected to the public sewage network or has an approved on-site system.

• Keep technical documentation, permits, and compliance certificates updated.

• Perform regular maintenance and inspections to prevent blockages or leaks.

• Respect the separation between rainwater and wastewater systems.

Compliance with these standards protects both your property’s value and public health.

In Summary

The General Regulation for Drainage Systems is a cornerstone of Portugal’s public health and building legislation. It guarantees that all buildings are equipped with adequate wastewater evacuation systems designed and executed by qualified professionals under municipal oversight. Its provisions apply to both new and existing buildings, promoting high sanitary and environmental standards.