The PURAIN filter series for rainwater and greywater harvesting

The PURAIN rainwater filters are usually dimensioned simply on the basis of the diameter of the connected rainwater collection line.*

If the diameter of the planned collection pipe is still unknown, the following table can be used as a guide. It gives an overview of the dimensioning of these rainwater connection pipes according to DIN 1986 at a design rainfall rate of r = 300 l/sha and a gradient of 1.5 %. The runoff coefficient indicates the factor by which the rainfall runoff volume can be reduced as a result of the roof type.

• Runoff coefficient 1,0 = theoretical value
• Runoff coefficient 0.8 = sloped hard roof
• Runoff coefficient 0.5 = extensive green roof

*The dimensioning of the greywater collection pipes for the use of the filter in greywater recycling systems can be found in the INTEWA Wiki.

For rainwater harvesting, PURAIN filters can be installed in most common cisterns, such as plastic, concrete, indoor and outdoor storage tanks. Many dealers deliver their tanks with PURAIN filters already installed. The PURAIN filters are also suitable for installation outside the cistern, if required. The PURAIN 150 and PURAIN HD filters are designed for direct buried installation. When installing the PURAIN filter, make sure that there is a height offset, even if small, between the inlet and outlet. For heavy rainfall areas and for greywater recycling systems, the PURAIN filters without weir are used in the type M design.

The PURAIN filters operate with minimum possible height offset between inlet and outlet. In a self-cleaning filter, such a height offset and the alternating jump principle are the only way for perfect operation. For very simple rainwater harvesting systems for garden irrigation and lower demands on water quality, we offer the collecting filter basket and the PLURAFIT filter with various inserts without height offset. These filters are particularly suitable for retrofitting rainwater harvesting systems for garden irrigation where no height offset is possible.