In order to provide drinking water of the highest quality at all times, water supply companies flush their drinking water pipes. The "condition-based flushing strategy" is now a procedure recognised by the German Technical and Scientific Association for Gas and Water (DVGW). DVGW Rule W 291 "Cleaning and disinfection of drinking water distribution pipes" was revised and published in December 2021. Compared to the previous version, it now includes, among other things, the findings and experience of TZW: DVGW-Technologiezentrum Wasser (German Water Centre) and of water supply companies on condition-based flushing strategy.
TZW has developed the method in recent years based on investigations in various research projects. This method is already being implemented by a large number of companies. The flushing strategy consits of the following steps:
- Development of a systematic flushing plan for the flushing area
- Carrying out a basic flush
- Repetition of the flushing after a defined interval with recording of the deposit situation in the pipes
- Calculation of the flushing intervals on the basis of the measured deposit situation
- Development of the condition-oriented flushing plan on the basis of the calculations
With this procedure, pipes are flushed when, after a certain period of operation, a critical deposit level is reached at which there is an increased risk of brown water or turbidity events. The reason for this is a mobilisation of deposits in the pipes. Practical experience shows that the occurrence of brown water can be reliably controlled with this targeted and sustainable approach. This is also proven by the experiences of the TZW as a result of the investigation of approx. 10,000 km of pipes in the context of supporting water suppliers in the implementation of the condition-based flushing strategy.
