GRAF detention cisterns for rain detention and channel relief

Detention systems, i.e. rainwater detention, play an important role in the reduction of hydraulic peaks and thus help relieve strain on the public sewer network, particularly in new construction areas. Detention systems usually consist of a volume which is used for the temporary storage of rainwater in the event of heavy rainfall, and a throttling device to limit the draining runoff water. The rainwater is cleaned using a filter before it enters the detention volume in order to avoid compromising the function of the throttling device. The throttled flow of rainfall is fed into the sewer and the excess amount is retained in the detention cistern. This amount accumulates in the detention cistern and is also drained off with the throttled runoff water after the rainfall event. The detention volume is thus discharged and remains available once more as a temporary storage tank for the next rainfall event.Advantages Carat XL detention cistern:


  • Suitable for HGV loading up to 12 t
  • Dome opening with stainless steel profile for precision fit and secure mounting
  • Can be mounted in groundwater
  • Lower weight than concrete and steel
  • Various connection surfaces DN 100 (4") / 150 (6")
  • Investment security thanks to a 15 year warranty


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

calculated size Request for information

Technical details


Earth covering with loading capacity [mm] 800 - 2000
max. axle load [t] 8
max. vehicle weight [t] 12
max. vehicle weight with reinforced concrete slab [t] 60

Groundwater installation

Earth covering with groundwater installation [mm] 500 - 1800


max. earth covering [mm] (without groundwater, vehicle loading) 2000