PURAIN 4″ Pre-Filters


If you are looking for a self cleaning filter with maximum capture efficiency, the PURAIN Jump Filter is for you. The key to the design of Intewa’s PURAIN filters is the hydraulic jump. Up to a certain rainfall rate, rainwater capture is 100%, something no other self cleaning filter can claim. Due to varying rainfall intensity, the actual capture efficiency varies with geography but in all regions most rain falls at low intensity.


When hydraulic jump occurs, the filter screen is naturally and vigorously cleaned. This happens several times a year with a properly sized filter.  When this happens, manual cleaning is unecessary.  Please refer to this blog post for proper filter sizing for your area.

The hydraulic jump simulates what happens in a stream when water flows over a drop caused by stones.  The intense turbulence flushes out debris and leaves the filter screen clean and ready for the next rainfall.




The PURAIN 4″ filters are usually an ideal size for single family homes.  Actual applicable roof size is dependent upon local rainfall intensity.  Click here for our sizing chart.

For example, the PURAIN DN100 will work well for a 3,500 square foot roof in Santa Fe, New Mexico or on a 1,500 square foot roof in Austin, Texas.



Other Important features:

  1.  Meets ASPE 63 stadnards for rainwater pre-filtration
  2. Easy to install with gasketed fittings for 4″ pipe.
  3. Skimming overflow and rodent proof reject port, so no need for separate devices.
  4. Can be mounted inside tanks or externally.
  5. Self cleaning with no need for separate cleaning shower like in competitive filters.

PURAIN DN100 Specification Sheet

PLURAFIT DN100 Calming Inlet Spefication Sheet

Our most popular residential filter with a 4″ inlet size. Comes with rodent proof feature and tank skimming overflow.  PURAIN Price List




Economically priced 4″ filter with tank skimmer, no rodent proof device. PURAIN Price List

Here are some additional resources on the Intewa PURAIN pre-filter series:

Comparison of 4″ PURAIN to other self cleaning filters – See how PURAIN Jump Filters blow away the competition in capture efficiency and self cleaning!

PURAIN Brochure



Technology Overview

Technical Data

PURAIN filter DN100 with skimmer and non-return valve

L x W x H: 23.7″ x 5.4″ x 11.3″
D1 Feed: 4″
D2 Accept to Cistern: 4″
D3 Reject: 4″
H1 Intake: 6.45″
Δh elevation loss between feed and reject 2″
Width of wedge wire filter: 800 Microns
Efficiency: 98%
Material: PP, EPDM, Stainless steel
Weight: 5.2 Lb