Areas of application


Areas of application

BIO-BLOK® rainwater drywells generally have these areas of application:

  • As a substitute for a stone drywell.
  • As a buffer for seepage of rainwater from heavy rain showers.
  • Where the rainwater quantity can be reduced through seepage.
  • With new development areas that are to be connected to an existing system with an insufficient pipeline capacity or rainwater pipe.
  • In existing properties subject to ground flooding, and where the natural solution is to build a retarding or seepage system.
  • With new developments/extensions instead of connections to an existing sewer system.
  • With drainage of paved areas, such as car parks.
  • With the renovation of existing old drywells (such as a stone drywell).
  • With new constructions where less dimensioning of pipes is requested in general and where the storage function can be covered by a retarding system.

It is important...

to consider where a rainwater drywell can discharge additional water when there is no space for the amount of rainfall in the drywell, so that what is shown here does not occur:

Overflowed rainwater drywell

The Danish Wastewater Committee has released a report with an estimate of how much rain we can expect in the future. The report indicates that an amount of rain that currently statistically happens once every 100 years may happen every 10 or 15 years in the future. A lot is expected from municipalities and sewage departments with regard to planning and ensuring that larger amounts of rainwater can be drained so that we can avoid flooded cellars, roads etc.

All drywells are dimensioned based on the drywell at some point overflowing, i.e. the drywell cannot hold the water quantity which enters it. It is thus just a matter of time before a drywell becomes overloaded.

If there are drywells which need to drain the roof water from a house, the drainage will normally take place from the lowest roof well. This roof well must therefore be placed such that the drained water will be unable to damage the surroundings. This means that the roof well must not be placed near entrance doors, light boxes or on ground where the water is unable to flow away from the house by itself.

If the drywells need to drain the rainwater from roads and car parks etc., it is very important to be prepared for what would happen when the drywell system becomes overloaded and where this would happen. It is of course not appropriate if there is water on car parks or roads for extended periods of time. The solution could be for drywells to be placed in green areas and they can drain the water into these areas. If this is not possible, an emergency overflow pipe to the closest wastewater pipe system might solve this problem. However, this must be done in consultation with the local pipework owner and the municipality.