Rainwater Harvesting Design
Supply of non-potable uses with rainwater
Project overview
Client: La Biscuiterie Namuroise
Location: Jemeppe-sur-Sambre, Belgium
Industry: Food and Beverage
Key Results
Rainwater system designed and installed
A complete harvesting, filtration, and distribution system supplies non-potable water from the building's roof to toilets and floor cleaning across the production facility.
Operational continuity guaranteed
Automatic top-up from the mains network ensures uninterrupted service during dry periods, with no manual intervention required.
Sustainable use of an existing resource
Large roof surfaces that previously discharged rainwater to waste now feed a 20 m³ underground storage tank, reducing reliance on treated drinking water for uses that do not require it.
The Challenge
A craft biscuit producer committed to sustainable operations, looking to make better use of what was already falling on its roof.
La Biscuiterie Namuroise produces artisan biscuits from recipes dating back to 1908, from its facility in Jemeppe-sur-Sambre. As a certified craft producer with an organic range, sustainability is part of the company's identity. The biscuiterie identified an opportunity to reduce its consumption of mains drinking water by capturing rainwater from its large roof surfaces and redirecting it to non-potable uses on site, namely toilet flushing and floor cleaning in the production area. A system was needed that could reliably deliver water of appropriate quality to each use point, handle seasonal variation in rainfall, and fit within an active production environment.
What Revalio Delivered
Revalio designed and installed a complete rainwater harvesting system, from collection through to distribution.
Collection and storage: Roof runoff is intercepted at the downpipes on the west side of the building and channelled to a 20 m³ underground concrete tank buried beside the canteen building. A foam pre-filter upstream of the tank removes organic matter and debris collected on the roof before water enters storage.
Pumping and treatment skid: A pre-assembled skid installed in the canteen room handles suction, treatment, pressure maintenance, and distribution. A Grundfos Scala 2 pump draws water via a floating suction kit to avoid disturbing sediment at the base of the tank. Water then passes through a 100 µm coarse filter, a 10 µm fine filter, and an activated carbon stage to remove dissolved organics and prevent taste or odour issues. A chlorine dosing pump provides the final disinfection step, ensuring microbiological safety for floor cleaning in the production area.
Distribution: The treated rainwater is distributed to three points: the two toilets in the canteen building, a cleaning tap at the centre of the production floor, and the four toilets in the main building.
Mains back-up: During extended dry periods, the tank refills automatically from the mains network, ensuring continuous service at all times without any manual intervention.
How the Solution Works
The system is sized around two key constraints: enough roof area to supply the daily demand, and enough storage to bridge dry periods.
With a minimum monthly rainfall of 46 L/m² in April and a minimum connected roof area of 370 m², the collection potential comfortably covers the daily demand of 770 litres across all uses. The 20 m³ useful storage volume provides four weeks of autonomy, covering the typical duration of a summer dry period. When that buffer runs low, the mains top-up kicks in automatically, with separate meters tracking both rainwater consumption and mains supplement volumes.
Results
✓ Complete rainwater harvesting system designed and installed, from roof collection to point-of-use distribution.
✓ Non-potable uses across two buildings supplied with harvested rainwater: six toilets and a production floor cleaning point.
✓ Four-week autonomy achieved through a 20 m³ underground storage tank, with automatic mains back-up for dry periods.
✓ Multi-stage treatment train installed, including coarse and fine filtration, activated carbon, and chlorine dosing.
✓ Separate metering of rainwater and mains consumption, enabling ongoing monitoring of water savings.
How to reuse rainwater?
Rainwater falling on large roof surfaces is a free, local resource that most industrial and food production sites send straight to the drain. With the right collection and treatment system, it can reliably supply toilets, cleaning, and other non-potable uses year-round. Talk to our experts about what your roof could be doing for you.