Cysts In Water: What Are They and How Do They Get There?

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Both groundwater (underground) and surface water supplies are susceptible to contamination from a group of microorganisms called cysts.

Cysts are waterborne parasites that get into water supplies due to contamination from sewage, agricultural runoff, and direct contamination from fecal matter.

Here, we’ve shared all the information you should know about cysts in water, including how they get there, their potential health effects, how to test for them, and more.

๐Ÿ“Œ Key Takeaways:

  • Cysts are single-celled organisms that cause waterborne disease when they’re ingested in drinking water.
  • Giardia, cyclospora, and cryptosporidium are the three most common cysts found in drinking water supplies.
  • You can test for cysts by sending a sample of your water to your local certified laboratory.

โ” What Are Cysts In Water?

Cysts are protozoans and single-celled organisms that contaminate raw surface water supplies, like rivers, lakes, and streams.

Three of the most common types of cysts that are found in drinking water are giardia, cyclospora, and cryptosporidium:

  • Giardia cysts are caused by a hardy parasite called giardia lamblia. These cysts cause a gastrointestinal illness called giardiasis (also known as “beaver fever”), with symptoms including diarrhea, vomiting, and stomach pain. The most common cause of giardia contamination is raw sewage contamination. Waste from beavers, muskrats, other water-dwelling animals, and animals that roam near water sources, may also cause giardia contamination.
  • Cryptosporidium cysts are caused by the cryptosporidium parvum parasite and enters surface water sources through leaking septic waste, runoff from farmland, and direct animal waste contamination. These cysts cause a waterborne disease called cryptosporidiosis if they’re ingested, which has mild symptoms including watery diarrhea and vomiting.
  • Cyclospora cysts are caused by a protozoan parasite called cyclospora cayetanensis and cause a mild gastrointestinal disease called cyclosporiasis. This illness is spread in contaminated food and water, and mostly spreads due to poor hygiene, rather than being passed from one person to another.

Cysts are rarely life-threatening in water, but drinking these microbes may cause gastrointestinal upset.

Cysts in water

๐Ÿšฐ How Do Cysts Get Into Water?

Cysts get into a surface water supply through contamination from the feces of infected animals and humans.

There are a few different ways that this contamination can occur:

  • Through runoff from farms and agricultural sites
  • From a leaking or overflowing septic system
  • From treated or untreated sewage
  • From wildlife that uses the water source

Cysts are most likely to contaminate lakes, rivers, and other surface water supplies because surface water is exposed to the elements and more prone to flooding and runoff.

Groundwater (underground water) sources, on the other hand, are less likely to be contaminated with microbial cysts because their water quality is more consistent and isn’t usually affected by changes above the ground.

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

Cysts are invisible in water, which means you can’t detect them in your drinking water supply by taste, smell, or appearance.

Unfortunately, that means that you could drink contaminated water and not be aware of it – or, at least, not until you started to experience the symptoms of waterborne disease.

The only way to know whether or not your drinking water contains microbial cysts is to look at testing data.

If you get your water from a city supplier, check your most recent Water Quality Report.

A Water Quality Report (or Consumer Confidence Report) provides data on which contaminants have been detected in your local drinking water supply. So, if any cysts were detected in your water, they should be listed in the Report, along with the concentration range detected.

Or, if you use a private well water supply or you want to confirm the validity of your water utility’s testing, you can pay for a laboratory test for cysts in drinking water.

We’ve shared more information on lab testing for cysts later in this guide.

Water possibly containing cysts

๐Ÿค” Are Cysts In Drinking Water Dangerous?

Different cysts have slightly different health risks when they’re ingested in drinking water. However, for the most part, cysts aren’t dangerous – despite their unpleasant gastrointestinal effects.

If a person with a healthy immune system ingests microbial cysts in their tap water, they may experience the following symptoms:

  • Diarrhea
  • Gas
  • Stomach cramps
  • Nausea
  • Vomiting
  • Dehydration
  • Loss of appetite
  • Weight loss

Cysts may be more dangerous – potentially even life-threatening – to a person with a compromised immune system.

Immunocompromised people might experience symptoms for a longer period (up to 30 days) chronic illness, or damage to the digestive tract or respiratory tract, depending on the type of cysts ingested.

๐Ÿ“‰ Are Cysts In Tap Water Regulated?

Yes, cysts in tap water are regulated. The Environmental Protection Agency (EPA) has various Health Advisories for cysts in public water systems, requiring water utilities to regularly monitor their water for these microorganisms and employ a suitable method of cyst removal if they’re detected.

Public water systems are evaluated by public health officials, which also inspect the performance and operations of water treatment plants. These inspections are used to evaluate the effectiveness of a water utility’s cyst reduction methods.

If your local water supply becomes contaminated with large concentrations of cysts and these microorganisms aren’t effectively removed at the plant, a temporary boil water notice might be issued. You can kill the majority of cysts by bringing your water to a rolling boil for 1 minute.

Your water utility will inform you when the boil water notice is lifted and your water is safe to drink as it comes out of your taps.

Testing for cysts in water

๐Ÿงช How To Test For Cysts In Tap Water

There are no effective DIY methods for testing for cysts in tap water. The testing process for any microorganism is complex and can’t be carried out with the traditional test strip and color chart kit.

The only way to effectively test for cysts in your water is to purchase a laboratory water test.

Laboratory testing is highly accurate and thorough, and should tell you the exact concentration of cysts in your tap water sample.

Water testing with tap score

You’ll be able to choose between tests for certain types of cysts (test packages for giardia and cryptosporidium are common), and comprehensive tests that detect cysts and other related contaminants in a water source, including other microorganisms, chemicals, and heavy metals.

To use a laboratory test for cysts detection, follow these steps:

  1. Order your preferred laboratory test and wait for it to be shipped to your home.
  2. Take a sample of cold water from your kitchen faucet and follow the test instructions to package the sample for posting.
  3. Return the sample to the laboratory.
  4. Wait for your water sample to be analyzed. You’ll usually receive the test results within 10-14 days.

If you’re really concerned about cysts in your water (for instance, if someone in your home has fallen ill and you have reason to believe that your water supply is to blame), switch to bottled water or boil your water while you wait for the test results.

๐Ÿ“– What To Do If You’re Concerned About Cysts In Your Water

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

  • If your water is treated by a municipal supplier, it should technically be safe from cysts contamination because there should be adequate water treatment facilities to remove these microorganisms if they’re detected.
  • If your local water utility uses inadequate chlorination systems or poorly-maintained filtration equipment, you’re at more risk of drinking cysts-contaminated water. Reach out to your water utility if you have any reason to be concerned.
  • Unfiltered water supplies in private wells are unlikely to contain cysts, but you should test your well water if you believe cysts contamination is probable. You can then look at methods to remove cysts if these parasites are detected in your water.
  • Don’t forget that there are other ways to contract waterborne diseases from cysts (see the below section), so your drinking water might not always be to blame.
Getting filtered water from an RO system

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

There are a few other ways that you might be exposed to cysts aside from ingesting them in your drinking water:

  • By swimming in water sources (such as lakes, streams, or swimming pools) that are contaminated with cysts
  • By eating foods that have been contaminated with cryptosporidium or giardia germs
  • By being in contact with or touching infected animals
  • By having close contact with someone who has recently been infected by the disease (only for giardia cysts)

๐Ÿ“‘ Final Word: Removing Cysts From Water

If you’ve discovered cysts in your drinking water and it falls on you to make your water safe to drink, don’t worry – you have options.

There are a few different ways to reduce, inactivate, or remove cysts from water:

We recommend looking for a water filter that has an official NSF Standard 53 or Standard 58 certification for cyst reduction or removal, or has at least been third-party tested to any of these Standards.

And, regardless of the filter that you choose, make sure it has plenty of positive feedback – both by expert reviewers and other customers – so you know for sure that you’re spending your money wisely.

  • 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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