Natural Swimming Pool Froschloch

Sportwelt Dortmund GmbH
Execution time:
2007 to 2008
Service phases:
1 - 8
Building costs:
approx. 1.7 MEuro
Planning Fees:
280,000 Euro


The Froschloch outdoor swimming pool in Dortmund Hombruch was first opened in June 1927. At that time, the pool was fed with water from the Kirchhörder Bach stream, which at that time still ran next to the pool on the premises of the swimming pool.
In the 2nd World War, the bath was completely destroyed during a bombing raid. In the 1950s, the outdoor pool was rebuilt and reopened in 1959. In the following decades, repairs and renewals were necessary again and again, until in August 2005 the pipes finally burst apart and the cracks in the basin could no longer be repaired.
Since 2008, the Froschloch has been converted into a natural outdoor pool and completely rebuilt, including the buildings.

Description of the Bath

The Froschloch outdoor swimming pool was in need of major renovation in its former state. The need for renovation concerned both the pool fabric (leaks), the technical pool water treatment (filter, disinfection, pool hydraulics), as well as the condition and design of the open spaces. In the course of the renovation, the buildings were also to be re-organised in terms of their functions and adapted to today’s leisure-oriented user behaviour. Especially the sanitary facilities and the gastronomic areas were to be upgraded and adapted to today’s standards. For structural reasons, the old building had to be completely demolished and rebuilt.

Today, the swimmers’ pool has four 25m lanes and is separated from the non-swimmers’ area by a central walkway. Underneath this footbridge is a surge tank that collects the discharged water from the overflow channels of both the basins, which is then conveyed to the Neptune filter via feed pumps.

In the new non-swimmers’ pool, the classic geometric pool shape with a shallow water side running in an arc was removed, creating new space for a spacious sandy beach.
The shallow water area is also sandy and invites the little bathers to play.
Another new non-swimmers’ pool with massage jets was created with a slight difference in height so that it is possible to slide to the lower region. A separate water world with a sprinkler field, play stream and shallow paddling area has been created for the little ones. Derived from the crescent shapes, this area is also called “Aqua-Luna”.
In the wider open space, there is now new play and climbing equipment, as well as a ropeway for the slightly older children. However, scattered wooden lounging platforms also offer quiet retreats for reading and sunbathing.

Water treatment

The water treatment system of the Froschloch outdoor swimming pool is a water-irrigated soil filter of the “Neptun” type. This was planted with marsh and reed plants for aesthetic reasons. The pool water treatment via the Neptune filter which has a surface area of 1,200 m² and is designed for a nominal number of 1,700 bathers/day.


  • Total water surface: 1,470 m²
  • Total water volume: 2,300 m³
  • Usable water surface: 1,470 m²
  • Water treatment: Neptune filter (1,200 m²), PO4 adsorber
  • Control: PLC, remote maintenance
  • Nominal number of bathers: 1,700 bathers / day
  • Annual visitors: 90,000 bathers / year