Rainwater harvesting in Belgium: why install a tank?

With heavier rainfall events and the need to preserve water resources, harvesting rainwater is a worthwhile solution for a home or a commercial building. A tank stores the water collected on the roof for reuse in applications that do not require drinking water.

Rainwater is free. Harvesting it reduces drinking water consumption for certain uses and limits the volume sent straight to the drainage networks. The benefit depends, however, on rainfall, roof area, storage volume and the building's consumption.

In a properly designed installation, rainwater serves for watering, outdoor cleaning, washing certain equipment and, depending on the design and the applicable rules, flushing toilets or other non-potable uses. It must not be treated as drinking water without suitable treatment and monitoring.

Water is collected on the roof, directed to the tank and filtered before storage. A pump then distributes it to the points of use. A complete installation includes a strainer or pre-filter, a tank, a pump, level control, filtration and safety devices.

There is no universal volume. Sizing takes into account the roof area actually connected, local rainfall, the number of occupants, the intended uses and the frequency of dry spells. A tank that is too small empties quickly; an oversized tank is a wasted investment.

No. Rainwater harvesting complements the drinking water network: the building must keep a backup supply when the reserve is insufficient. Any interconnection that could pollute the public network must also be avoided. In Wallonia, CertIBEau pays particular attention to tanks and to connections between mains water and rainwater.

Rules differ between the three Regions. In Wallonia, rainwater and planning requirements are checked per project and municipality; the Water Code gives priority to managing rainwater on the plot, with infiltration as the first option where conditions allow. In Flanders and Brussels, specific rules on tanks and rainwater management also apply.

A harvesting installation needs periodic maintenance: checking the pump, cleaning the filters, inspecting the tank, pipework and distribution. This is what preserves the quality of the stored water and the reliability of the whole system.

Weber Water studies your rainwater harvesting installation, from collection to pumping and distribution, to size the tank and pump correctly for the building's actual uses.