Note

Septic tanks in Spain: discharge rules

§ 1Where the rule comes from

Wastewater from a rural home that is not connected to a sewer needs a destination, and the destination is regulated by the river basin authority because it can affect rivers and groundwater. We read the published requirements of the Segura basin authority for discharge from single-family homes and small settlements. They apply the national rules in that basin, and other basins may differ. This page belongs to the chapter on the rules on rural services.

§ 2Authorisation or a sealed tank

According to those requirements, discharge from a single-family home, or from a site that produces only sanitary wastewater, to surface water, to groundwater or to the ground needs authorisation, and treatment must come first. No authorisation from the basin authority is needed if the wastewater goes to a sealed tank, made of a material such as polyethylene or concrete, that a licensed waste manager empties regularly, removing wastewater and sludge. Discharge to a municipal or regional sewer is authorised by the local or regional authority.

§ 3Treatment options

The authority describes a conventional system with a project signed by a competent technician, or a prefabricated unit that meets a European standard, with a CE marking, a declaration of performance and a maintenance manual. For small prefabricated systems it gives minimum removal rates and a minimum capacity, and it says these are guidelines that it can change depending on the receiving environment. For an existing unit, it asks for the invoice and photographs. An installer should give you a certificate.

§ 4Land and sewer

The requirements say the applicant must own the land the system occupies or crosses, or else a cadastral plan is needed for an easement. They also say discharge to the public water domain is not allowed if a connection to the municipal sewer is feasible, and that the authority will consult the town. Stormwater and pool drainage must not go through the treatment system.

§ 5Vulnerable groundwater

The authority may require a hydrogeological study for discharges to groundwater and it classes groundwater vulnerability with named methods. A home above a vulnerable aquifer may face stricter requirements. The page we read gives no setback distances from wells or watercourses, so ask the authority for any that apply, and note that a well on your plot, as wells and water explained explains, is affected by your own discharge.

§ 6Buying a home with a tank

Ask the seller for the authorisation or the contract with the waste manager, the certificate of the unit, the emptying records and the plan of the system. If none exists, treat the home as having an unauthorised discharge and ask your lawyer to resolve it before completion. Buying a home with a well explained explains the contract points for a well, which are similar.

§ 7Costs and care

Budget for a certified unit, installation, authorisation, emptying and maintenance. We found no official prices. A tank that overflows is a health problem and a legal one.

§ 8What we could not verify

We read one basin authority’s requirements and not the national regulations or the rules of other basins. Local rules on tanks in towns also vary.

§ 9More on this topic

Off grid Electricity rural Spain explains grid connection and off-grid power for a rural Spanish home.

Legal note. How the process works in general. It is not legal advice, and it never replaces an independent Spanish lawyer acting for you.