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Giardia / Cryptosporidium

Giardia / Cryptosporidium

Giardia and Cryptosporidium can be removed by using modern water filtration equipment without the need for chemicals or power in most cases with the cysts being trapped by the filter.

What are Giardia and Cryptosporidium?

Giardia and Cryptosporidium are our most commonly found protozoa in water tanks. Giardia is a diarrheal illness caused by a one-celled, microscopic parasite, Giardia intestinalis (also known as Giardia lamblia). Once an animal or person has been infected with Giardia intestinalis, the parasite lives in the intestine and is passed in the stool. Because the parasite is protected by an outer shell, it can survive outside the body and in the environment for long periods of time.

During the past 2 decades, Giardia infection has become recognized as one of the most common causes of waterborne disease (found in both drinking and recreational water) in humans in New Zealand. Giardia are also found worldwide.

How does Giardia and Cryptosporidium get in my water tank?

The Giardia parasite lives in the intestine of infected humans or animals. Millions of germs can be released in a bowel movement from an infected human or animal.

Most homes in New Zealand have birds and occasionally possums getting on your house roof. These animals poo all over your roof, it then rains and washes the poo into your tank. There can be millions of cysts in a single poo from 1 bird or possum. If the conditions are right in your tank then you will have these cysts living in your tank and potentially coming from every tap in your home.

Here is the question “would you get on your roof and lick off the bird and possum poo?” no I didn’t think so, now if you haven’t got any water filtration why are you prepared to drink it?

What are the symptoms of giardia?

Giardia infection can cause a variety of intestinal symptoms, which include:

*Gas or flatulence
*Greasy stools that tend to float
*Stomach cramps
*Upset stomach or nausea.

These symptoms may lead to weight loss and dehydration. Some people with giardia have no symptoms at all.

Should I have my tank water tested?

Tests used to specifically identify Giardia are often expensive, difficult, and usually require hundreds of litres of water to be pumped through a filter. Consider generally testing your tank for fecal contamination by testing it for the presence of coliforms or E-coli instead of Giardia. Although tests for faecal coliforms or E-coli do not specifically tell you whether Giardia is present, these tests will show whether your tank water has been contaminated by faecal matter.


Ultraviolet Sterilization 

This is the most cost effective and efficient method For the treatment of Biological contaminated water containing "faecal coliforms" caused by Birds,Opossums on exposed gutters and Live stock faecal run off into streams or shallow Bores.

UV water disinfection is a natural process which does not add any chemicals into your water, nor alter the water chemistry. Ultraviolet light energy inactivates harmful microorganisms such as bacteria and viruses by disrupting the DNA, effectively preventing them from multiplying and causing illness. The pathogens are destroyed in the time water passes through the disinfection chamber. E-coli, Cryptosporidium and Giardia are examples of waterborne microorganisms that cause numerous gastrointestinal illnesses which are easily controlled with UV disinfection.

Please see our UV systems available:

Other Options Include

(As noted from the Centres for Disease Control & Prevention-

Boiling Water:

To kill or inactivate Giardia, bring your water to a rolling boil for one minute (at elevations above 6,500 feet, boil for three minutes) Water should then be allowed to cool, stored in a clean sanitized container with a tight cover, and refrigerated.


Not all home water filters remove Giardia. Filters that are designed to remove the parasite should have one of the following labels:

  • Reverse osmosis
  • 1 micron or less