Bus washing plant

Hanau, Germany | 1992

One of the very first rainwater harvesting systems that WISY manufactured for a major industrial client was installed in Hanau. The city buses operated by the Hanauer Strassenbahn GmbH have been washed with soft rainwater since 1992. The rainwater is harvested from a 1,080 m² sized section of the workshop building roof. The average annual rainfall of 650 mm provides enough rainwater to wash 70 buses per week so that passengers can have the pleasure of travelling in sparkling clean vehicles!

The operator of the bus washing plant uses the lime-free rainwater for the last washing cycle. All of the water used to wash each vehicle (around 2,000 litres) is collected up again and cleansed. It is stored for future washing operations in three plastic tanks (each with a capacity of 2,000 litres) installed in the service room. Water lost from the circuit during each washing operation is always replenished from a 2 m³ top-up tank.

The rainwater harvesting system is equipped with six downpipe filters that are connected to three downpipes (two filters per downpipe). The filtered rainwater is stored in a 40 m³ underground tank and pumped when required into the top-up tank in the service room.

Object Data

Annual rainfall [mm = litres / m²]
Roof surface [m²]
Cistern capacity [m³]



40 m³ underground tank, in-situ concrete
2 m³ buffer tank


6 x WISY-Filter Collector Special Edition, mesh size 0.28 mm, always two pieces on top of each other.


Bus washing plant