This is an official online service provided by the
Wisconsin Department of Safety and Professional Services





Plumbing Products Register

Contaminant: Bacteriostasis

Bacteriostasis is a term that is frequently misunderstood by consumers and sometimes misrepresented in the marketplace.  The suffix “–stasis” means the state of equilibrium, balance or stagnancy.  Thus the term bacteriostasis means to hold bacteria in a state of equilibrium, balance or stagnancy.  The suffix “–cidal” means of a killer or killing, or that can kill.  Thus the term bacteriocidal means to kill bacteria.  Do not confuse the meaning of bacteriostasis with bacteriocidal.

A bacteriostatic water treatment device is a device designed to limit the passage, or growth, or both, of heterotrophic bacteria so that the bacterial population of the filtered water is not larger than that of the unfiltered water.  Notice that a reduction in the number of bacteria is not required for a device to qualify for bacteriostasis.  Thus, a bacteriostatic water treatment device has the ability to inhibit the growth of the bacteria without necessarily destroying the bacteria.  Upon loss of contact with a bacteriostatic material, bacterial growth may rapidly return.  Heterotrophic bacteria occur naturally and do not typically cause disease in otherwise healthy people.  However, some heterotrophic bacteria may pose a health risk for individuals with a compromised immune system, and some are opportunistic pathogens. For further information on the potential adverse health effects of naturally occurring heterotrophic bacteria, consult the following:

The crucial point to remember regarding bacteriostatic water treatment devices is that such devices will not make microbiologically unsafe water safe to consume.  A water treatment device approved for bacteriostasis simply means the device, and more specifically the filtration media within the device, will not support bacterial growth.

Examples of bacteriostatic materials commonly used within water treatment devices are silver and copper/zinc filtration media.  A primary focus of this department, when reviewing a bacteriostatic water treatment device, is to determine the if any of the bacteriostatic material is being released into the filtered water stream, at health effecting concentrations, by the device.

For additional information on microbiological safety, consult:

Continue to Bacteriostasis listings pageGo back to Contaminant listing web page