Filtering effectiveness: It's all about microns!

The micrometer or micron (μm) is unit of length equalling 1×10−6 metre, which is one millionth of a meter or one thousandth of a millimeter. Here are examples of some micron sizes:

  • A red blood cell is typically 8 μm.
  • A width of a strand of spider web silk is typically 3 - 8 μm.
  • A white blood cell is typically 25 μm.
  • A human hair is on average 70 μm.
  • A grain of table salt is approximately 100 μm.

A micron rating for a water filter indicates the ability of the filter to remove contaminants by the size of the contaminant's particles. The higher the micron number the larger the filtration pores.

Bacteria range in size from 0.2 to 2 microns in width or diameter and from 1 to 10 microns in length for the non-spherical specie. The common Escherichia coli (E. coli) is a rod-shaped bacterium where each bacterium measures approximately 0.5 μm in width by 2 μm in length. Vibrio cholerae (Cholera) is also a rod-shaped bacterium, measuring 0.3 μm in width and 1.3 μm in length. Viruses are typically 0.004 to 0.1 microns in size, which makes them about 100 times smaller than bacteria.

Bearing this in mind, one should seek a filter with a smaller micron number for better filtering capability; the larger the micron number, the less effective the filter in removing health threatening contaminants.

The Sydney 905 Filters ® prove to be one of the fastest, easiest, effective and most cost efficient ways to get safe water. These water filters use hollow fibre (Polysulfone) membranes.

There are two types of filters available for sale:

  • With the 0.1 micron (absolute) pore size filter, it is impossible for any bacteria, protozoa or cysts to pass through this microfiltration filter. This is the company's standard filter. It has been tested by Umgeni Water which is SANAS accredited. Membrane area is 0.5m (nominal value).

As the pores of the membranes within the Sydney 905 Filter are 0.1 microns in size, this means 700 pores can fit, side by side, in a width of a single human hair or approximately 10 000 will fit into a millimeter.

  • If viruses are an issue, then with the 0.01 micron (absolute) pore size purifier, it is impossible for viruses in addition to bacteria, protozoa and cysts to pass through this ultrafiltration purifier. This is the company's premium filter. This purifier is known to block even the smallest know virus to man which is the MS2 virus. However, the flow through this membrane is slow due to this absolute pore size and thus it is recommended to be configured within a pressurised system. Membrane area is 0.61m (nominal value).

As the pores of the membranes within the Sydney 905 Purifier are 0.01 microns in size, this means 7000 pores can fit, side by side, in a width of a single human hair or approximately 100 000 will fit into a millimeter.


Simple Design and Construction- This is as simple as it gets. Families are able to setup and adapt their filter in minutes. The filter merely has to be attached to a threaded connection or onto a non-threaded connection via the supplied universal adapter and then it is ready for use.

Fast Flow- This is a Point of Use System (POU). The 0.1 micron filter can be gravity fed or can handle up to just over 4 bars of pressure which will give about 100 litres per minute.

There is a high flow rate of the filter and this flow rate is determined by a combination of:

  • Head pressure (The distance from the top of the water to the filter).
  • Pump used.
  • Altitude (The higher the altitude, the slower the flow rate).
  • How clean the filter is.
  • The filter itself (there are variations between the two filters).

The 0.01 micron purifier will ideally need a pressurised supply of water due to its microscopic pore size. It will give about 10 litres per minute at around 4 bars of pressure.

Extremely Long Lasting and thus cost effective - Maintenance of the filter is very simple. When the filter starts to slow down, one simply needs to backwash it with clean water using the syringe provided in the kit. Since the filters can continuously be backwashed and re-used, they have an extremely long life expectancy, making them self-sustainable and dependable. There is no need to replace the filter cartridge if good care is taken in looking after them, thus making them truly sustainable.

Portable- They are small enough to easily be moved around and/or used in different applications.

Multiple Applications- These filters make water so clean and accessible that people will not only use the filtered/purified water for drinking but also for cleaning, bathing, cooking and more. There are multiple configurations of use such as on rainwater harvesting tanks, buckets, bottles, taps etc.