Skip to content
My WebMD Sign In, Sign Up

HIV & AIDS Health Center

Font Size

You Can Prevent Cryptosporidiosis

How Can I Protect Myself from Crypto? continued...

B. Filtering tap water: Not all available home water filters remove crypto. All filters that have the words "reverse osmosis" on the label protect against crypto. Some other types also work, but not all filters that are supposed to remove objects 1 micron or larger from water are the same. Look for the words "absolute 1 micron." Some "1 micron" and most "nominal 1 micron" filters will not work against crypto. Also look for the words "Standard 53" and the words "cyst reduction" or "cyst removal" for an NSF-tested filter that works against crypto.

To find out if a particular filter removes crypto, contact NSF International (3475 Plymouth Road, P.O. Box 130140, Ann Arbor, MI 48113-0140; telephone 1-800-673-8010; fax 313- 769-0109), an independent testing group. Ask NSF for a list of "Standard 53 Cyst Filters." Check the model number on the filter you intend to buy to make sure it is exactly the same as the number on the NSF list. Look for the NSF trademark on filters, but be aware that NSF tests filters for many different things. Because NSF testing is expensive, many filters that may work against crypto have not been tested. Reverse osmosis filters work against crypto whether they have been tested by NSF or not. Many other filters not tested by NSF also work if they have an absolute pore size of 1 micron or smaller.

If you choose to buy a filter, look for this information on the label:

Filters designed to remove crypto (any of the four messages below on a package label indicate that the filter should be able to remove crypto)

  • Reverse osmosis (with or without NSF testing)
  • Absolute pore size of 1 micron or smaller (with or without NSF testing)
  • Tested and certified by NSF Standard 53 for cyst removal
  • Tested and certified by NSF Standard 53 for cyst reduction

Filters labeled only with these words may not be designed to remove crypto

  • Nominal pore size of 1 micron or smaller
  • One micron filter
  • Effective against giardia
  • Effective against parasites
  • Carbon filter
  • Water purifier
  • EPA approved -- Caution: EPA does not approve or test filters.
  • EPA registered -- Caution: EPA does not register filters for crypto removal.
  • Activated carbon
  • Removes chlorine
  • Ultraviolet light
  • Pentiodide resins
  • Water softener

Filters collect germs from your water, so someone who is not HIV infected should change the filter cartridges for you; if you do it yourself, wear gloves and wash your hands afterwards. Filters may not remove crypto as well as boiling does because even good brands of filters may sometimes have manufacturing flaws that allow small numbers of crypto to get past the filter. Also, poor filter maintenance or failure to replace filter cartridges as recommended by the manufacturer can cause your filter to fail.

WebMD Public Information from the CDC

Today on WebMD

HIV Myth Facts
Slideshow
STD Overview
Article
 
smiling mature man
Article
AIDS retrospective slideshow
Slideshow
 

HIV AIDS Screening
Slideshow
man opening condom wrapper
Quiz
 
HIV AIDS Treatment
Feature
Discrimination Stigma
Feature
 

Treatment Side Effects
Feature
grilled chicken and vegetables
Article
 
obese man standing on scale
Article
cold sore
Article
 

WebMD Special Sections