## Waste water drainage

The wastewater discharge Qww according to DIN EN 12056-2, is determined from the sum of the connected loads (DU), taking into account the simultaneity, where K is the guide value for the discharge coefficient. It depends on the type of building and results from the frequency of use of the drainage objects. Qww – wastewater discharge (calculated flow) K – discharge coefficient DU – connection value of unit Qtot – total wastewater discharge Qs – continous wastewater discharge (without simultaneity reduction) From the sum DU, the wastewater discharge Qww can be calculated with the above formula, taking into account the corresponding discharge coefficient K. If the determined wastewater discharge Qww is smaller than the largest connected value of a single drainage object, the latter is decisive (limit value).

## Rainwater drainage

r5/2 Five-minute rainfall, which statistically must be expected once in 2 years r5/100 Five-minute rainfall, which statistically must be expected once in 100 years

DIN 1986-100 lists the values for several German cities as examples. The values differ from r5/2 =200 to 250 l/(s ha) or r5/100 = 800 l/(s ha) [1 ha = 10,000 m²]. Information on rain events is available from the local authorities or alternatively from the German weather service. Reference values are given in DIN EN 1986-100 Annex A. If no values are available, rT(n)=200 l/(s ha)should be assumed. For economic reasons and in order to ensure the self-cleaning capability, pipe systems and the associated components of the rainwater drainage system shall be dimensioned for a mean rainfall event. In the scope of DIN 1986-100, the calculated rain is an idealized rain event (block rain) with a constant rain intensity over 5 minutes. The annuality (Tn) to be used for each design case is determined by the task definition. Rainfall events above the calculated rainfall (r5/2) are to be expected as planned. Qs – Rainwater drainage (calculated flow) rT(n) – Dimensioning value according to statistical events C – Characteristic coefficient for type of drainage area A – Size of drainage area

## Pumped medium in wastewater technology

During dimensioning, care must be taken to ensure that explosion-proof units are used to convey sewage containing faeces from shafts connected to the public sewer system. See for example also UVV 54.Kanalisationswerke: §2 The sewer system, its access points, wells, shafts and rainwater inlets as well as collection points and venting valves in the pressure pipe system are considered to be potentially explosive in their entirety … resp. explosion protection guidelines (Ex-RL) of the professional association (GUV 19.8) edition 06.96, example collection no. 7.3.1.1. There are, however, other regulations that may have to be taken into account. You can obtain more detailed information for your specific case from the trade association, the trade supervisory authority, the TÜV or the building authority.