GRAF stores water for nursery flowers

Posted by Callum Vallance-Poole, on July 15, 2021.

Gräfin von Zeppelin nursery uses two Carat XXL plastic tanks with 144,000 l volume for watering

A colourful carpet of flowers greets visitors from afar, from spring to autumn. Hardy perennials are grown on 5 ha in the perennial nursery Gräfin von Zeppelin in the Markgräflerland region of southwest Germany. More than 2,500 species and varieties are sold in the local nursery in Sulzburg-Laufen and the nursery’s own mail-order business. For watering the plants alone, some 36,000 litres are needed every day. In addition to water from its own springs, the rainwater from the greenhouses and production buildings is stored. The roof drainage from two newly constructed buildings is stored in two GRAF Carat XXL plastic tanks, each with a capacity of 72,000 litres.

The Gräfin von Zeppelin perennial nursery is one of the oldest and best-known nurseries in Germany. In 1926, Helen Gräfin von Zeppelin, the aviation pioneer’s niece, inherited the Meierhof vineyard estate, picturesquely situated in the vineyards of the Markgräflerland, from her grandmother and founded a nursery after studying at the Lehr- und Forschungsanstalt für Gartenbau (Teaching and Research Institute for Horticulture) in Berlin-Dahlem. This third-generation business with more than 40 permanent employees and many seasonal workers is run by Frederik von Rumohr as managing director and Michaela Rösler as operations manager.

The nursery is very busy in the best sense of the word: featuring on television, in renowned garden magazines and represented at garden festivals in Germany, France and Switzerland. Visitors flock to events like the Gräflich Zeppelinische Garden Festival. The readings, seminars and workshops are just as popular as the Lilies Café in the sales greenhouse. The nursery has long been a destination for bus tours.

Even though complementary accessories, books, gardening tools and garden clothing have long been offered, the team around manager Michaela Rösler concentrates on what has been the success of the nursery for over 90 years now: the extraordinary variety and multiple award-winning quality of the perennials. First and foremost, the 300 varieties of irises, 150 different peonies and 250 varieties of daylilies. Another speciality of the Gräfin von Zeppelin perennial nursery are the ready-planned bedding ideas for various locations, which are available as a complete package with planting and care instructions.

The Markgräflerland is one of the sunniest and warmest regions in Germany with an average of over 1,700 hours of sunshine per year. The western slopes of the Black Forest protect against excessive drought. The Atlantic clouds get stuck here, before releasing the rain they hold. This means that there is usually sufficient summer rainfall, which promotes growth in the region.

Roof drainage for watering

Despite the good growing conditions, the flowers for sale on the planting tables require a lot of water. For watering, a widely ramified network has been created, which is fed from the nursery’s own springs and rainwater stored in cisterns from the roof drainage system. This is gradually being renewed and expanded.

The course area is also constantly being renewed and expanded. For example, two buildings with a floor plan of 44 x 14 m were recently built. These are used for production and the booming mail-order business. The 1,500 m² roof area of the buildings is drained via DN 200 collection pipes to the two GRAF Carat XXL underground tanks, each with a capacity of 72,000 litres. Up to 144,000 litres of rainwater are stored in them. In addition, the drainage pipe for collecting the slope water is fed into the two tanks – 6,000 litres per hour. The two tanks are connected to each other to ensure an even water level when feeding and drawing off.

The required storage volume, the topographical conditions, the existing infrastructure and the restricted access in the village and in the nursery initially placed what were thought to be high demands in terms of the installation of the tanks. The operations manager, together with the planner Hans-Jochen Mönch and the local building contractor Dörle Bau, who carried out the work, decided in favour of the plastic tanks from GRAF for several reasons.

Tanks lifted in 40 min without heavy-duty crane

It was possible to transport the two tanks to the site without the expense of special transport and to lift them over a building to the installation site using a conventional crane. Due to the low weight of the plastic tanks, no heavy-duty crane was needed for this, unlike with cisterns made of concrete or steel. Such a crane could not have been used due to the constricted access and the stability and topography of the ground. Each of the tanks was lifted from the truck into the excavation pit in just 20 minutes.

Despite the significantly lower weight compared to tanks made of concrete and steel, the ribbed construction of the tank ensures a high level of stability. With an earth covering of just 1 m, the GRAF Carat XXL plastic tank can be driven over by a vehicle weighing up to 40 t. The fact that the plastic tanks could be driven over was another plus point for the operations manager. Due to the existing site structure, the tanks were installed underneath the yard area used by vehicles. The yard areas will later be covered with a greenhouse.

The sturdy tank can also be installed in groundwater up to its midway point. As a mark of its high quality, GRAF offers a 30-year warranty on the XXL tank.

The coordinated individual components of the system saved the contractor Dörle Bau GmbH, Sulzburg, time and money during installation. The excavation of the pit (19.55 x 9.40 x 3.80 m) in loose loess soil, the construction of the gravel bed (3.60 m depth) were carried out in only 3 working days. The pit was backfilled with 8/16 gravel up to 20 cm above the shaft body, the covering was made with RC 0/45 gravel up to the ground surface and 8 cm high concrete paving was laid over it.

The GRAF telescopic dome shafts are continuously height-adjustable and inclinable by 5 degrees. The cast iron telescopic dome shaft can be installed in a paved or tarmac yard. The iron telescopic dome shaft for trucks allows conventional cast concrete covers to be used.

As an option, the tank can be fitted with an extra tank dome. The Carat XXL comes as standard with connection surfaces up to DN 200. If required, connectors up to DN 300 can be factory-fitted on the tank dome and face end.

GRAF Carat XXL in 18 different sizes

The Carat XXL underground tank is available in 18 different sizes with capacities ranging from 16,000 to 120,000 litres. Because of its modular concept, the tank can be used for the storage and retention of rainwater, as a reservoir for process and fire-fighting water and as a septic tank for local wastewater.

Marketing Coordinator - Based at our UK HQ in Banbury, Oxfordshire, Callum is responsible for promoting Water Management Systems, Attenuation Tanks, Treatment Plants, Rainwater Harvesting Systems and more!