Distance requirementsRainwater drywells must be located a minimum of 25 m from drinking water boreholes and the distance to watercourses, lakes or the sea must be at least 25 m. The distance to watercourses, lakes and the sea can be reduced if a discharge permit can be granted by the municipality. A discharge permit is subject to the recipient quality being observed and water catchments and groundwater resources not being polluted. In Danish Building Research Institute (SBi) instruction 185 on Drainage Installations and in DS 440, “Standard for small drainage systems with seepage”, the following distance requirement guidelines are laid down: The centre line of the drywell (longitudinal axis) and endpoints must be kept at least 5 m from residential properties with/without cellars. With non-residential houses the distance can be reduced to 2 m. The recommended distance requirements are illustrated below:
Recommended distance requirements from drywell to either building or boundary
The distances stated must be observed for buildings on the actual site and also for existing and future developments in the neighbouring site. Taking the risk of steeping into consideration, the drywell must not be brought closer than 2 m from the boundary.
It should be noted that these are recommended distance requirements and must also depend on a specific evaluation of each case. The specific evaluation can be carried out by, for example, an authorised sewerage contractor; however, the actual distances must always be approved by the municipality. If it can be proved that the risk factor is very low when installing a drywell 2-3 m from a residential property this should not be a barrier to the installation. This can be possible, for example, in one or several of the following circumstances:
- ♦ If the ground falls away from the house.
♦ If the house is new.
♦ If, on an existing property, a layer has been installed for blocking rising soil moisture.
If on the existing soil conditions there is no risk of steeping, or if the neighbouring site remains undeveloped, the distance requirement to the boundary can also be reduced.
The distance requirements are listed in the table below:
in acc. with
SBI 185 or
| Drinking water
| Residential property
|-||5 m||2 m *)|
property with cellar
|-||2 m||2 m *)|
property without cellar
|-||2 m||1 m *)|
|Boundary||-||2 m||0,5 - 1 m **)|
*) If the ground falls away from the property, if the building is new or if on an
existing property a layer has been established for blocking rising land moisture.
**) If the soil conditions ensure there is no risk of steeping, or if the neighbouring
land remains undeveloped.