Wavin WiseDrop

Urban water management is under pressure from several directions at once, and passive detention was not designed to carry that load on its own.

• Flood risk: The annual amount of rainfall remains roughly the same, but the rainfall pattern is changing. Climate change and rising temperatures mean the atmosphere can hold more water, resulting in long dry spells in summer and very heavy downpours when it does rain, along with long wet periods in winter. Passive tanks sized against historical assumptions cannot adapt when conditions shift beyond that point.
• Water scarcity: Longer dry periods raise the cost of potable water for non-potable uses, and the pressure to reuse rainwater is rising.
• Capacity constraints and urbanization: Underground space is contested and shrinking while impervious surfaces keep growing. Installing separate tanks for attenuation and reuse is often impractical on dense sites. The existing underground drainage was designed on the knowledge and assumptions available at the time, and those expectations were considerably more optimistic, so the sewer system cannot cope with the increasing runoff caused by the expansion of paved areas.
• Regulatory pressure: Discharge consents are tightening, sewer fees are climbing, and SuDS, BREEAM, and LEED increasingly expect documented performance.
• Lack of visibility: A passive tank offers no real-time data on level, performance, or discharge compliance, which creates reporting gaps and maintenance blind spots.

Passive tanks are highly effective during storms, but they are mostly empty in between, and they deliver no insight into how they are performing. Their capacity is often calculated on the basis of exceptional rainfall, which makes the investment substantial. The gap between what stormwater infrastructure is now expected to do and what passive systems can deliver is the reason the market is moving from passive delay to active, forecast-driven control.

✅A real-world challenge
During the 2025 expansion of the Humboldt School in Oberlungwitz, Germany, the town faced exactly this situation. The Lungwitzbach stream that receives the site’s stormwater was already heavily loaded even during minor rainfall, so a conventional throttled discharge was not an option. At the same time, the school and the town wanted to reuse rainwater for the school garden, but limited space ruled out building any additional storage.

Two operating modes, one tank

• Green mode (maximize reuse): WiseDrop keeps rainwater in the tank for as long as it is safe to do so, based on weather forecast and sensor data. When the forecast rain is more than the available capacity, it drains just enough water before the rain comes to free the capacity needed. Captured water is available for irrigation, toilet flushing, and other non-potable uses.
• Blue mode (attenuation): When reuse is not required, for example when there is no irrigation demand in winter, WiseDrop catches rainwater to reduce sewer load and releases it in a controlled way some hours after the rain stops, to keep sewer capacity available.

Note: It is possible to configure when the system operates in green or blue mode through the year, depending on the project requirements.

✅How this played out in Oberlungwitz: The WiseDrop Controller connects the sensors and the flow-control chamber to Wavin iConnect. Using hyperlocal weather forecasts and live sensor data, iConnect makes predictive decisions and automatically controls the outflow, deciding whether to retain rainwater for reuse or release it in a controlled way to free capacity ahead of rain.

The storage tank itself remains a proven civil asset, so its core flood-protection function does not depend on the smart layer being perfect. The controller runs on 230 VAC with a UPS backup for power-loss situations.

Operational

• Automatic operation based on forecast and sensor data.
• 24/7 remote monitoring, automatic alerts and remote manual override through Wavin iConnect.
• Open APIs to connect to third-party systems.

Environmental

• Reduces combined sewer overflow events by managing when water is released.
• Supports rainwater reuse that offsets potable water for non-potable applications.
• Helps return captured rainwater to a more productive, circular use.

✅Proof: flood risk and reuse: In Oberlungwitz, WiseDrop enables proactive, situation-dependent discharge that specifically relieves the Lungwitzbach stream during small and medium rainfall events and reduces peak flows. The rainwater stored in the Q-Bic Plus system is used to water the school garden, and the local fire brigade was given access through a suction point for training and as a reserve in case of major fires.

Financial

• Reduces water costs through reuse.
• One tank instead of two lowers capital cost and saves underground space.
• Supports higher certification ratings that can improve asset value.

✅Proof: funding and space: Because the Oberlungwitz solution combines several functions in one multi-functional system, the project qualified for European funding, which significantly reduced the town’s contribution. The town achieved both attenuation and reuse without building any additional storage, an important advantage where underground space is limited.

Infrastructure resilience and water management

• The same attenuation volume serves both flood protection and reuse.
• Forecast-driven control adapts to changing rainfall patterns.
• Compliance is achieved with less volume and minimized off-site drainage, while capacity is protected ahead of storms.
• Because the tank remains a conventional storage volume, core flood protection is preserved.

Every project has different stormwater requirements. WiseDrop is the intelligence layer of a broader Wavin water management portfolio, and it is designed to actively manage the storage and infiltration systems below it. The Oberlungwitz project shows this in practice, where WiseDrop controlled a Q-Bic Plus system to combine attenuation and reuse.

Product descriptions are general portfolio context. Confirm current specifications and naming for AquaCell 400, Q-Bic Plus LC, PolderRoof, and TreeTank against their own product pages before publishing.

WiseDrop is most powerful as part of a system. Use these combinations as a guide when scoping a project.