The GRAF Retention cistern combines rain retention with rainwater harvesting.
To guarantee retention of rainwater, a delayed drain is fitted in the channel with 0.05 to 2.0 l/sec. depending on the customer’s specifications and the retention or harvest volumes. In the event of heavy rainfall, the water level in the cistern rises above the max. water level (short term) and is drained into the channel at delayed speed using a floating drain choke.
This relieves the channel and the treatment works.
The water level can rise to the emergency overflow and sinks slowly back down again after the rain to the long-term max. water level. This rainwater can then be harvested.
We also construct and supply individual, special solutions.
Sizes between 3,750 – 100,000 l with corresponding retention volumes are possible.
This special type of rainwater harvesting is prescribed or subsidised in many communities.
- For rainwater retention
- For rainwater harvesting in the house and garden
- For frost-proof installation in the ground
- The entire tank volume can be used for rainwater retention
- "USA Patent 7854338"
Mini telescopic dome shaft with lid, suitable for pedestrian loading
order no.: 371010
Maxi telescopic dome shaft with lid, suitable for pedestrian loading
order no.: 371011
Telescopic dome shaft with cast iron lid, suitable for vehicle loading
order no.: 371020
Telescopic dome shaft TRUCK
order no.: 371021
Telescopic dome shaft TRUCK for concrete rings
order no.: 371003
Choke drain package detention/retention
order no.: 369020
For underground tank Carat 0,05 - 2,0 l/s, DN 100 connection, 3 m hose