PURAIN Hydraulic Jump Pre-Filters


Self-cleaning PURAIN pre-filters have the highest rainwater capture with exclusive hydraulic jump technology patented by Intewa.

Using the unique jump filter design, PURAIN filters catch 100% of rainfall up to a certain flow rate.  At higher flow rates, the filter is vigorously cleaned using what is called a hydraulic jump action.  This leads to the highest overall water capture efficiency regardless of geography.  You will be surprised how clean your filter is and how much water you have collected!

PURAIN filters have superior technology:

100% Capture

  • At most rainfall rates, all the water that enters the PURAIN filter goes through the ASPE 63 compliant screen and into the cistern.  We have checked this for all areas across the USA, from the light rainfalls of Seattle to the deluge prone areas of Florida.  The result is the same.  Almost all rainfall the falls is at a low flow rate of less than about 1″ per hour.

Hydraulic Jump

  • At higher flow rates, water capture rate is maximized while a hydraulic jump forms.  When this occurs all accumulated debris is flushed out of the filter and the screen is vigorously cleaned.  We size PURAIN filters to reach hydraulic jump at least a few times a year so that they are virtually maintenance free and always capture the maximum amount of water.




  • 800 Micron Wedge Wire Screen
    • The PURAIN screen meets ASPE 63 standards and delivers higher flow of clean water to the tank than the other leading self-cleaning filters.
  • Integrated Skimmer
    • The 4” and 6” PURAIN filters have an integrated skimmer to assure great water quality in the tank.
  • Heavy Duty Construction
    • The 8” to 16” filters have a heavy duty option for direct burial, meaning the added cost of a vault is eliminated. With their very sturdy and robust construction, PURAIN reaches the deepest direct burial depth (without a vault) of any leading rainwater inlet pre-filter with up to 7’6” depth and 60 ton vehicle loading possible.
  • Minimal Elevation Loss
    • In many applications, elevation loss from inlet to overflow is important.  All PURAIN filters have elevation loss of less than 1 pipe diameter.  This also allows for in-tank installation to provide many additional benefits.
  • Smart Design  
    • This makes installation easy. Easy installation minimizes costs in any configuration.   You can install PURAIN filters easily inside tank, outside tank, directly buried, even for retrofits.  Easy connections make installation a breeze.

The PURAIN rainwater inlet pre-filters provide technical superiority at competitive price to other products on the market.  They have better water capture, almost non-existent maintenance, and easier installation which leads to far lower life-cycle cost compared to any other competitive filter.

Contact us to get more information about our comprehensive range of PURAIN hydraulic jump filters.  With sizes from 4″ inlets for residential scale projects to 16″ inlets for commercial scale, Intewa’s PURAIN has you covered.  You will notice that our price is very competitive with all other self-cleaning filters.  For more details on these superior products, click here for the Intewa USA website.


DN100 Thumb

4″ Residential


DN150 to DN400 Thumb

6″ to 16″ In Tank or External


HD Thumb

6″ to 16″ Below Ground