Self-cleans with 98% efficiency

  • Self-cleans with 98 % efficiency

Light rainfall

Light rainfall events account for over 97% of total annual rainfall. Therefore, it is particularly important to collect this light rain. With the PURAIN hydraulic jump filter, water is trapped in the trough, filtered and delivered into the tank. The trough ensures that no precious water is lost.

Heavy Rainfall

Heavy rainfall events, that occur approx. 4 to 10 times a year, contribute only about 3% to total annual rainfall and are used by the PURAIN rainwater filter for self-cleaning. This heavy rainfall leads to the formation of an eddy in the PURAIN rainwater filter, the so called hydraulic jump. The hydraulic jump is powerful enough to pickup debris accumulated in the trough and discharge it to the overflow.

The PURAIN rainwater filter cleans itself during heavy rainfall events. That means minimum maintenance for the user in comparison to other filter systems and unique for a self-cleaning rainwater filter, a filtering efficiency of 98%. 

With PURAIN filter, water is collected in a trough, which is then filtered and delivered into the tank. The trough ensures that no precious water is lost. 3.5 kg of sand-gravel mixture was flushed away in just 30 seconds (see photo) due to the efficiency of the hydraulic jump.

Please also refer to the report with a filter comparison test.


The possibility to save drinking water has enhanced strongly the last years.

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A rainwater filter cleaning itself by the principle of the hydraulic jump.

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The DRAINMAX tunnel infiltration system: The only plastic trench with flushable  ground.

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The optimized water pump station for rainwater and greywater utilization in every planned construction.

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Tel. +352 (0)2695 811 1

E-Mail: info[at]


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