Rainwater harvesting: how to use the water from your tank wisely

Harvesting rainwater is one thing; using it properly is another. A well-designed installation clearly separates water intended for non-potable uses from public network water, and ensures reliable distribution to the various points of consumption.

The obvious uses are those that do not need drinking water: watering, outdoor cleaning and certain household uses permitted by the installation design, such as toilets. In a business, harvested water can also serve for certain cleaning or technical uses where sanitary and regulatory conditions allow.

Water collected on a roof can contain dust, particles, organic matter, micro-organisms or substances from the roof and the environment. Without treatment specifically designed and monitored to produce drinking water, it remains non-potable.

This is the essential point. The rainwater network and the drinking water network must never be connected in a way that could contaminate the public network. In Wallonia, CertIBEau highlights the health risk of a connection between the mains water circuit and the rainwater circuit.

The pump is the heart of distribution: it must deliver the flow and pressure the points of use require. Its choice depends on the height to overcome, the pipe length, the number of draw-off points and the pressure sought. An automatic control starts it when a tap opens and stops it when demand ceases.

A well-thought-out installation provides a backup: automatic top-up or switchover to mains water, with hydraulic separation compliant with the rules. The aim is to maintain service without creating a dangerous link between the two networks.

Upstream filtration limits matter entering the tank and protects the pump; additional devices exist depending on uses. But filtration that protects the installation must be distinguished from treatment that would make water drinkable: they are not the same objectives.

A tank that is never checked accumulates sediment, filters clog and the pump loses performance. A periodic check verifies the quality of storage, pump operation, levels and safety devices.

The best system is not the biggest. Sizing seeks a balance between water availability, storage capacity, flow, pressure, installation cost and maintenance. A preliminary study avoids oversized or ill-suited equipment.

Weber Water supports you in designing and maintaining rainwater harvesting installations: filtration, pumping, control, distribution and servicing.