Detention cistern for rainwater detention and sewer relief

  • A detention cistern retains the rainwater and drains it into the sewer at a delayed speed.
  • GRAF cistern for rainwater detention and sewer relief.
  • To guarantee retention of rainwater, a delayed drain is fitted in the sewer with a delay of 0.05 to 16 l/sec. depending on the customer’s specifications.
  • In the event of heavy rainfall, the water level in the cistern rises above this level and is drained into the sewer at a delayed speed using a floating drain choke. This relieves the sewer and the treatment works. The water level can rise to the emergency overflow and sink slowly back down again after the rain.
  • Sizes between 1,500 – 7,500 l with corresponding retention volumes are possible. 
  • We also construct and supply individual, special solutions.


Volume [l]Length [mm]Width [mm]Height [mm]Weight [kg]Retention volume [l]order no.add to enquiry

calculated size Request for information

Technical details


Earth covering with loading capacity [mm] 700 - 1000
max. axle load [t] 2.2
max. vehicle weight [t] 3.5
max. vehicle weight with reinforced concrete slab [t] 60

Groundwater installation

Earth covering with groundwater installation [mm] 700 - 1200


max. earth covering [mm] (without groundwater, vehicle loading) 1200