Collection: Ster-O-Tap Information

The Ster-O-Tap water sterilization cartridge consists of a bundle of hydrophillic (water loving) capillary membranes. These membranes are shaped like hollow fibers, closed on the feed side. The water follows a path from the large pores on the outside wall to the small pores on the inside wall. The inside wall of each fiber has very tiny pores - 0.15 microns in diameter (0.00015 mm). These pores are several times smaller than the smallest bacteria, which is about 0.4 microns in diameter. When water flows through these pores, an unparalleled removal of >99.999999% (8 log) of all bacteria is achieved. This prevents harmful bacteria and cysts (like e-coli, crypto and giardia) from reaching your faucet and provides you the protection you need.

The patented Ster-O-Tap low pressure membrane technology achieves this remarkable micro filtration with extremely high flow rates at low feed pressure. There is very little pressure drop as with other technologies, such as ceramic. It requires less than 14 psi for a 1 gpm flow.

Ster-O-Tap capillary membrane cartridges have been tested and certified by the NSF International against ANSI/NSF Standard 42 for Particle Reduction (Class 1) and ANSI/NSF Standard 53 for Cyst and Turbidity reduction.

Ster-O-Tap® Membrane Features


Capillary membrane with asymmetric micro-porous structure, internally skinned
o Very high flow rates at low pressure gradients
o Narrow consistent pore size ranges
- micro filtration  0.15 micron 
o High surface porosity and overall porosity (> 85%)
o Permanently hydrophilic with neutral surface charge for low fouling characteristics.
o Withstand feed- and backwash pressures up to 7 Bar - > 105 PSI
o Chemical resistant to allow for a wide range of cleaning agents, incl. chlorine
o Heat resistant up to 120 oC (248 oF)


A Ster-O-Tap®  Micro (MF) filtration cartridge is composed of a bundle of many capillary membranes, which are sealed in a housing, with the membranes closed on the feed side. The feed water follows a path from the large pores on the outside wall to the small pores on the inside wall for high flow rates at low pressure (US Patent: 5.895.573 - European Patent: 97942301.9)


Electron Microscope photos of  Ster-O-Tap®  capillary membrane

Cross section capillary membrane (156x)


Outside wall capillary membrane (5000x)



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