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.
  • We also construct and supply individual, special solutions.


Advantages Platin XXL flat tank:

  • Rotating tank dome to easily align the connecting lines
  • Available with a second tank dome as an option
  • Suitable for HGV loading up to a vehicle weight of 30 t (66138 lbs)
  • Flexible connection up to DN 300 (12")
  • Connection openings with prefitted DN 150 (6") lip seals
  • Tank height of just 125 cm (4' 1")
  • High-quality, integrated DN 150 (6") filter technology
  • Dome opening with stainless steel profile for precision fit and secure mounting
  • Connection fitting of up to DN 200 (8"), on tank dome of up to DN 300


Scope of supply: 

  • Platin XXL flat tank
  • Detention set: floating choke drain, outlet fittings with emergency overflow, DN 100 (4") connection

Not included in the scope of supply:

  • Matching cover
  • Installation of optional Platin XL/XXL detention/retention filter package 2


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

calculated size Request for information

Technical details


Earth covering with loading capacity [mm] 700 - 1300
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 - 1500


max. earth covering [mm] (without groundwater, vehicle loading) 1500