Giardia In Water

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Giardia cysts are one of the most common causes of waterborne disease. Surface water supplies are at risk of being contaminated with these microorganisms.

They’re caused by a parasite called giardia lamblia, which is hardy and can survive for long periods outside of the human body.

Here, we’ve shared everything you need to know about giardia in tap water, including what it is, how it gets there, how to test for it, and more.

๐Ÿ“Œ Key Takeaways:

  • Giardia lamblia is a parasite that causes a waterborne disease called giardiasis (sometimes known as “beaver fever”).
  • Giardiasis is a diarrheal disease that isn’t dangerous to most healthy people, but it can cause long-term health complications.
  • You can test for giardia cysts in your drinking water by sending off a water sample to a laboratory.

โ” What Is Giardia In Water?

Giardia (or giardia lamblia in full, also known as giardia duodenalis and giardia intestinalis) is a parasite that causes a waterborne disease called giardiasis.

This parasite can infect both humans and animals. Infection occurs when giardia is ingested in contaminated drinking water, food, surfaces, or objects.

Giardia cysts are hardy, with tough outer shells that enable them to survive in cold water for months on end. The good news is that unlike similar parasites (such as cryptosporidium), giardia can be effectively treated with drinking water chlorination.

Giardia is most commonly found in raw surface water sources, but it may also contaminate groundwater supplies.

giardia well water

๐Ÿšฐ How Does Giardia Get Into Water?

Giardia gets into water through numerous contamination routes.

Lakes, rivers, streams, and other surface water sources are the most likely to be contaminated by giardia because they’re open to the elements. There are a few different possibilities for giardia contamination:

  • Through agricultural runoff from sites with animals
  • Through direct contamination from animal feces
  • From an overflowing or leaking septic system
  • From sewage discharge (either treated or untreated)

Most wells are deep and sturdy enough to be protected from giardia contamination, but if the well is poorly designed or maintained, or is vulnerable to surface water contamination and flooding, giardia cysts may enter the water supply.

Shallow wells are more likely to be contaminated by giardia because they’re closer to the surface of the ground.

Once giardia has entered a water supply, it will remain there for long periods. If this water is used for public drinking water, it should be treated to kill the giardia cysts and make the water safe for human consumption.

๐Ÿ”Ž How To Know If Your Water Contains Giardia

Giardia is a microscopic parasite, which means you can’t see it in your water without using a microscope. Giardia also has no smell, color, or taste, so you won’t be able to tell the difference between clean water and water that is highly contaminated with giardia.

Unfortunately, in the case that you drink water containing giardia, you would probably only find out when you experienced some of the primary symptoms of giardiasis.

So, how do you know if your water contains giardia?

One option is to check your most recent Water Quality Report. Your local water supplier should produce an annual Water Quality Report (or Consumer Confidence Report) that shares which contaminants have been detected in your water. Even low levels of giardia should be noted in this Report if they were discovered.

You might not want to rely on your water utility to provide accurate or honest information about your water quality. Or you might get your water from a private well, which you are responsible for testing and treating.

In this case, you should consider buying a laboratory test for giardia in tap water.

You can find more information about lab testing later in this guide.

Water testing data sheet report

๐Ÿšฑ Is Giardia In Drinking Water Dangerous?

Giardia in drinking water isn’t usually life-threatening, but it’s still considered dangerous because it could make you sick. Different people will have different reactions to ingesting the giardia parasite, depending on the person’s immune response and the level of contamination.

If you have a healthy immune system, you might not even get any symptoms from drinking a small number of giardia cysts in your water. However, ingesting large amounts of giardia will usually result in giardiasis.

The symptoms of giardiasis appear within 3 to 25 days after untreated water is ingested and lasts for two to six weeks in the average healthy human. However, some people may develop chronic diarrhea that lasts for weeks or months, coupled with weight loss.

The symptoms of giardiasis include:

  • Watery diarrhea
  • Bloating
  • Nausea
  • Gas
  • Fatigue
  • Stomach cramps or an upset stomach
  • Weight loss

Itchy skin, hives, low-grade fever, and joint swelling are other, less common symptoms of this waterborne disease.

There are a few long-term health complications that may result from giardia infections, including irritable bowl syndrome, reactive arthritis, and recurring or severe diarrhea.

People with compromised immune systems (such as malnourished children, people receiving certain cancer treatment, AIDS patients, and organ transplant recipients) are more at risk of contracting giardiasis and experiencing the long-term effects of this disease.

Nausea after drinking water

๐Ÿ“‰ Is Giardia In Tap Water Regulated?

Yes, giardia in tap water is regulated. The Environmental Protection Agency (EPA) has enforced a Surface Water Treatment Rule, which requires all public water systems to filter and disinfect their water to remove or kill at least 99.99% of giardia cysts.

Under this Rule, water utilities must monitor their water supplies and take the necessary action if cysts are detected, such as flushing the system with chlorine, issuing a short-term boil water notice, or considering alternative methods of treatment for long-term drinking water safety.

Public health officials monitor and evaluate water treatment plants to entire that their methods of reducing or killing giardia are effective.

So, if you get your water from a public supplier, you shouldn’t – in theory – be at risk of giardiasis.

However, if you drink untreated water from a private well, your water isn’t regulated, and you will need to take your own action if you’re concerned about giardia contamination.

๐Ÿงช How To Test For Giardia In Tap Water

Testing water for giardia is a complex process that can’t be carried out with a simple at-home test kit.

The process usually involves filtering large volumes of water (between 10 and 50 liters), then inspecting the concentrated water sample to determine its giardia concentration.

As you can imagine, this isn’t something that you can do at home. If you want to test for giardia, you’ll need to send a water sample to an accredited laboratory for official testing – which will usually set you back hundreds of dollars.

Even then, the test results are limited because a single water sample might contain no cysts, but that doesn’t mean that none are present in your entire water supply.

Still, lab testing is as accurate as it gets, so if giardia cysts are present, your report will outline the exact concentration detected.

To use a giardia laboratory test, follow these steps:

  1. Choose an accredited water testing laboratory and order a giardia test kit.
  2. Wait for your kit to arrive, then follow the laboratory’s instructions to collect and ship your water sample back to the lab.
  3. Receive your test results (usually within 10-14 days).

If you have reason to believe your water contains giardia (for instance, if someone in your home is showing symptoms of giardiasis and you’ve ruled out other sources of the disease), we recommend switching to bottled water or boiling your water for at least 1 minute before drinking until you receive your test results.

tap score water testing

๐Ÿ‘ฉ๐Ÿฝโ€โš•๏ธ What To Do If You’re Concerned About Giardia In Your Water

If you’re concerned about giardia in your water, the action you should take depends on your specific situation:

  • If you get tap water from a municipal supplier, your water shouldn’t contain giardia because common water disinfection methods (like chlorination) should kill this parasite. However, if your water quality is compromised for whatever reason and/or giardia outbreaks occur, your water supplier should issue a temporary boil water notice while the problem is addressed.
  • If you get your water from a private well, in some unlikely circumstances your water could become contaminated with giardia cysts. Test your water if you have any reason to be concerned.
  • If testing your water reveals giardia, you have a few options. In the short term, switch to bottled water or boil all the water you plan to drink (by bringing it to a rolling boil for 1 minute). You might also want to look at long-term solutions, such as water treatment systems that offer cyst removal.
  • Make sure that contaminated water is to blame for the giardia infection, and not other sources (such as those listed below).

โš ๏ธ Other Ways You Might Be Exposed To Giardia

Although contaminated drinking water sources are most commonly to blame for giardia infection, there are a few other ways that you might be exposed to giardia cysts:

  • By swimming in recreational water sources (such as lakes, ponds, hot tubs, and swimming pools) that are contaminated with giardia.
  • By eating food contaminated with giardia (e.g. preparing food on a contaminated surface).
  • Through person-to-person contact.
  • Through touching contaminated surfaces or objects then touching your mouth.

๐Ÿ“‘ Final Word: Removing Giardia From Water

Thankfully, in our modern world, the likelihood of contracting giardia infection from your drinking water is low.

However, in some unlikely situations, your tap water might be compromised by giardia cysts. Or, you might be embarking on a hiking or camping trip where clean, pathogen-free water sources aren’t guaranteed.

In these cases, you can use a water filter system with a 1-micron absolute pore size to remove giardia from your water and make it safe to drink. If all else fails, boiling water for 1 minute will also do the trick.

๐Ÿ‘จโ€๐Ÿ”ง Other methods of removing or killing giardia in water include reverse osmosis, water distillation, and UV purification.

The best filters are tested to NSF Standard 53 or Standard 58, or have an official certification to these Standards, certification for cyst reduction or removal.

  • Jennifer Byrd
    Water Treatment Specialist

    For 20+ years, Jennifer has championed clean water. From navigating operations to leading sales, she's tackled diverse industry challenges. Now, at Redbird Water, she crafts personalized solutions for homes, businesses, and factories. A past Chamber President and industry advocate, Jennifer leverages her expertise in cutting-edge filtration and custom design to transform water concerns into crystal-clear solutions.

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