Types of wastewater
We distinguish between the following types of wastewater:
- Domestic wastewater, divided into wastewater without sewage (greywater) and wastewater with sewage (blackwater)
- Rainwater (precipitation water that has not been contaminated by use)
- Wastewater from grease separator systems
- Wastewater from light liquid separator systems
- Wastewater from rainwater harvesting systems
- Wastewater from small-scale sewage treatment plants
- Wastewater from drainage systems
This classification is therefore based solely on the quality and characteristics of the wastewater stream. The primary consideration is the maintenance of the functionality of the upstream discharge points. The type of use of the building and site in question is not a decisive factor. For instance, commercial or industrial premises may also generate wastewater that corresponds to domestic wastewater. These sub-streams must then be treated as domestic wastewater. Conversely, social facilities may also generate wastewater from commercial kitchens, for example. This sub-stream must then be treated as Grease wastewater.
In the case of sewage, attention must be paid to a further subdivision into greywater and blackwater. The use of backflow prevention systems for wastewater without sewage in the case of wastewater from toilet facilities is considered a design error and must be avoided. In backwater valves, this leads to a reduction in flow velocity, to deposits and consequently to malfunctions.
When selecting products, it is crucial to distinguish between wastewater without sewage and wastewater with sewage. The decisive factor is always the type of wastewater that drains through the backflow preventer towards the sewer.
- Wastewater without sewage (= greywater) consists of water without sewage, such as shower water or water from washing machines.
- Wastewater with sewage (= black water) is always present when pipes are connected that carry sewage from urinals or toilets in the direction of flow.
It is irrelevant which type of wastewater is forced back in the event of a backflow (i.e. from the sewer towards the backflow preventer)!
Covered damage will only be compensated if the correct type of backwater prevention device, in accordance with DIN EN 13564, has been installed. Furthermore, the volume of wastewater generated must be taken into account. With regard to flow rate, the design rules set out in DIN EN 12056 apply. The capacity and size of the backwater prevention system must be sufficient to handle the volume of wastewater generated.
