Tap water can’t test positive for Covid-19

4 January 2022
What was claimed

Tap water can return a positive lateral flow test result for Covid-19.

Our verdict

Putting tap water on a lateral flow test will break it. Claims that water has tested positive have no basis in fact, because the test is used incorrectly.

A number of posts on Facebook show people putting tap water on lateral flow tests, either to claim that Covid-19 could be present in the water supply or to suggest the tests don’t work. Some of the posts are screenshots of a tweet posted by musicians Right Said Fred.

Claims that tap water returns a positive result for Covid-19 on a lateral flow test follow the pattern of similar posts we have fact checked many times previously. Throughout the pandemic, posts which purported to show items such as fruit, cordial, Coca-Cola and ketchup testing positive racked up thousands of shares online. 

Some of the Facebook posts are videos showing people holding lateral flow tests under running water and subsequently returning a positive result. 

These videos do not show that tap water contains Covid-19, nor do they demonstrate that the tests do not work when used correctly, both of which could be potentially harmful pieces of misinformation if wrongly inferred from these posts. They simply show the person in the video incorrectly using, and therefore breaking, the test. 

As we have written before, the fact that these tests can be broken with food or drink does not make them inaccurate or unreliable for use in the general population. Lateral flow tests are unlikely to give a false positive result if used correctly (by swabbing the nose and/or throat and using the extraction buffer solution before dropping the sample onto the test).

A spokesperson for US lateral flow test manufacturer Abbott told Reuters that the tests being exposed to tap water were not being used as intended and that “other liquids have chemical properties which can cause a chemical reaction on the test strip, resulting in misleading or inaccurate results.”

There is no evidence Covid-19 can be transmitted through tap water. The UK’s Drinking Water Inspectorate has said: “In the UK, drinking water supplies are routinely disinfected as part of the treatment process, and this process removes all harmful pathogens including viruses. 

“The coronavirus Covid-19 is thought to spread between people who are in close contact with one another, and all evidence from the spread of the virus shows that the drinking water supply is not a route for transmission of the virus.”

The Right Said Fred tweet claims that two lateral flow tests conducted with tap water, taken 20 minutes apart, returned two different results—one positive and one negative. 

The only evidence presented for this is a picture of the tests presented side by side, so we can’t say for sure how the tests were carried out. However, the fact that tap water was used as the sample instead of a nasal swab means that they were not used correctly. 

As we have set out above this means the results of the test are unreliable and misleading. The fact that there are two different results does not tell us anything about the efficacy of the tests when used correctly. 

Dr Alexander Edwards, associate professor in Biomedical Technology at the University of Reading, previously told Full Fact on this subject: “If you completely ignore the manufacturer’s instructions or in fact use the test for something completely different, then you shouldn’t really be surprised if you get a silly result.”

This article is part of our work fact checking potentially false pictures, videos and stories on Facebook. You can read more about this—and find out how to report Facebook content—here. For the purposes of that scheme, we’ve rated this claim as missing context because the posts show lateral flow tests being used incorrectly, which leads to the testing kits breaking.

Full Fact fights bad information

Bad information ruins lives. It promotes hate, damages people’s health, and hurts democracy. You deserve better.