2
1. Introduction
Updated technical data, scope of application and basic dimensioning are available at:
https://za.intewa.net/en/products/purain/technology/
Various filter tests and reports are available for download at:
https://za.intewa.net/en/products/purain/downloads/
2. Technology and Scope of Application
Thank you for your INTEWA product purchase.
Your PURAIN Rainwater filter provides optimum rainwater quality in your tank.
PURAIN rainwater filters (also known as Hydraulic-Jump filters) deliver high performance in the
filtering of rainwater and this hydraulic-jump technology means that the filter cleans itself
automatically.
During the design phase, INTEWA studied world rainfall data. Purain filters have been designed to
collect rainwater especially from “light” rainfall events and use the “heavy” events for self-cleaning.
This efficient design is important, as studies have shown that 97% of all world rainfall comes from
“light events”, leaving only 3% of rainfall coming from “heavy events”.
+/- 97% of world rainfall is termed "light events" - (measured as less than .6mm in 5 minutes)
+/- 3% of world rainfall is termed "heavy events" - (measured as more than .6mm in 5 minutes)
As most other filters cannot adequately collect light events without wastage they end up with
collection efficiencies of between only 60 - 70%
– and waste large quantities of valuable rainwater.
By using this little-known knowledge, INTEWA has been able to design the world's first "hydraulic
jump" self-cleaning rainwater filter, offering the highest water collection efficiency of any filter
available. Rain filtering is all about
Quality & Quantity
!
In the design, the flow of water is substantially altered due to a height drop, from a sub-critical to a
super-critical flow. At the bottom of the collection chamber, the water flow alters again to a subcritical
flow in a process now commonly known as a hydraulic jump. This resulting increase in water power
is similar to a strong eddy and forces any impurities into the overflow to be washed away to waste.
Independently tested
by Germany’s Siegen University, the PR-150-S is rated as one of the most
efficient rainwater filters in the world - at 98% collection efficiency. This means that for every 100
