what does it all involve?

Having a septic tank in Spain

25 / May

A septic tank is an underground liquid-proof tank in which wastewater is stored and converted into odourless and inert substances by bacteria. A septic tank is used in areas that do not have access to sewerage and is made of different materials such as concrete, fibreglass or plastic. The septic tank separates the organic waste that sinks to the bottom as sludge,from the fats, oils and greases that float to the surface.

To find out whether it is legal to install a septic tank in Spain, one must consult local regulations and always follow the procedures laid down therein regarding: the design, construction, maintenance and proper use of the tank. Moreover, environmental and health regulations should be observed to avoid soil and water pollution as much as possible.

Details on the location of a septic tank

The septic tank is installed where toilet and kitchen/laundry waste (black and grey water) is produced, and is usually located in the yard of a dwelling. However, some details about the location must be taken into account before the municipal license is issued. The regulations of the respective municipality elaborate on this, but in general terms the rule is that there is no municipal sewerage system in the immediate surroundings. In addition, the tank must be between 5 and 8 metres from the house and other dwellings or buildings. It should also be at least 30 metres away from risk areas such as wells, puddles and streams, etc. For irrigated areas (crops, orchards, etc.) and water sources (rivers, lakes), the distance should be at least 50 metres.

Different types of septic tanks

There are municipalities that do not allow the installation of septic tanks but do allow the installation of watertight tanks. Septic tanks contain a filter, while watertight tanks do not. As a result, these tanks have to be emptied by specialised technicians.

In contrast, so-called septic tanks have a drainage trench that filters “grey” water (wastewater without chemicals and bacteria) that is then filtered through the soil. Septic tanks without a filtering trench are used for “black” wastewater that does contain chemicals and bacteria that are dangerous to humans and the environment. These tanks are required to be emptied by licensed technical specialists.

What are the necessary administrative actions to install a septic tank?

As soon as you know you want to install a septic tank on your plot, you must inform the municipality. What they will require depends on each municipality, but the following are almost always required:

  • Building license (Licencia de obra). This licence covers the project to construct and operate the system. The document should include: the size, location, brand and models of equipment to be purchased, capacity, quotation, implementation period, etc;
  • Inspection of the installation (Seguimiento de la instalación). Once the municipality has approved the license, the septic tank can be installed. The work process can be followed by the municipality to verify that the entire project presented is carried out as stated;
  • Certificate of completed works (Certificado Final de Obra). This should be submitted to the municipality when the installation is completed;
  • In addition, if the tank has a drainage ditch where wastewater is discharged into the soil, a license must be applied to the Hydrographic Confederation (la Confederación Hidrográfica) of the area where the tank is located. This application must include an explanatory report detailing the characteristics of the project and the origin of the water.

 Applicable legislation

The applicable legislation ranges from European, national, regional to municipal level and all these legislation, especially the latter, will condition the possibility of installing a septic tank. This legislation mainly regulates urban planning, the environment, hydrography and territorial planning.

According to the law, septic tanks are only allowed if there is no sewerage system in the immediate surroundings of the plot. While the autonomous comunidades are competent in environmental matters and regulate the installation of septic tanks because of their ecological impact on the natural environment, on the other hand, it is the municipalities that have the final word, as they are responsible for the tank requirements, safety, sewerage, etc.

In many rural houses, the septic tank is a necessity. Its installation, cleaning and maintenance have to be carried out according to a special protocol established by the administrations, which in many cases requires professionals or qualified experts to deal with everything to do with septic tanks ( besides having the necessary licenses for it, as I mentioned above).

In short, to know whether it is legal to have a septic tank on your plot, each case must be examined individually taking into account the local legislation of the respective municipality. To this end, you have to study the regulations of the municipality where the septic tank is located and, if necessary, be informed beforehand by an engineer from the planning department of the relevant municipality.

If it is not possible to install a septic tank, the alternative is a watertight tank. Unlike a septic tank, a watertight tank does not filter; the waste water must therefore be removed by a special tank truck. The installation of these tanks is almost always permitted and to succeed in this, the details specified in the applicable regulations are sufficient to obtain the required permit; usually a license for small-scale works (licencia de obra menor).

It is very important to remember that if you live within 100 metres of a sewerage system, it is always compulsory to connect to it.

Penalties for illegal septic tanks

If the above regulations, maintenance, etc. are not complied with, the government will impose sanctions on septic tanks declared illegal because of the risk they pose to humans and the environment. These sanctions are laid down in the Water Law (la Ley de Aguas), which is included in Royal Decree 1/2001. Although the cost of the sanction can be up to a million euros in the worst case, in a normal case, the financial penalties for an illegal septic tank do not exceed 7,000 euros (this does not include the cost of any damage caused by dumping in the public/private domain).

The offences of an illegal septic tank are:

  • Unauthorised construction; as installation of septic tanks requires a series of steps to be followed;
  • Illegal dumping of wastewater;
  • Pollution of public water;
  • Failure to comply with all other obligations under the Water Act.

If you have any doubts or concerns about the legality of your septic tank or the applicable penalty regime, do not hesitate to contact Lex Foris International Law.

Rafael Montes Velástegui