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Can you catch COVID-19 through your plumbing system?

Stay six feet apart. Practice excellent hygiene. Stay home. We’re all aware of the basic measures for preventing the spread of the coronavirus pandemic. But are there means of transmission we haven’t considered yet, like through the water or sewage pipes in a house or apartment building?

According to the Center for Disease Control, analysis of prior coronavirus outbreaks, including SARS and MERS, revealed that coronaviruses can be transmitted through the sewage system, impacting plumbers and tenants alike. But the current science on the specific coronavirus that causes COVID-19 indicates so far that the risk of this new virus infecting people via plumbing is quite low.

Nonetheless, if you’re in an apartment building or other multi-tenant dwelling and you want to take extra precautions with your plumbing, here’s a list of tips to prevent COVID-19 transmission through your pipes:

  • Dry pipes are a potential source of contamination, so keep your pipes from getting dry by periodically pouring water through floor drains in bathrooms, garages, and basements
  • Beware of odors coming from a drain as a sign of dry pipes
  • The toilet U-trap should be filled with 0.2-o.4 gallons of water, while sinks, bathtubs, showers, and other fixtures need up to 1-2 gallons depending on the model
  • Clean and disinfect bathroom fixture surfaces in a two-step process using an antiviral non-toxic solution
  • Handle overflowing toilets quickly to avoid fecal contact, and eliminate any standing water
  • Don’t leave septic tanks uncovered or broken
  • Routine plumbing inspections are key to catching problems that could spread COVID-19

The risk in apartment buildings

While no coronavirus cases during this epidemic have been confirmed by spreading through the sewage, there are suspicions about one apartment building in Hong Kong. The apartment was partially evacuated in February after officials feared plumbing was to blame. Two residents in a high rise called Hong Mei House had contracted coronavirus by that point, and three cases were later reported as well. The two original victims’ apartments were vertically aligned ten stories apart, CNN reported, and their toilet discharge pipes were linked.

Plumber Stephany Smith works with London-based plumbing company My Plumber, part of the big Fantastic Services family, which operates on three continents (Europe, USA and Australia). She has some concerns about the virus being transmitted in certain conditions, and she’s been researching extensively to protect herself, and others in the industry from harm during the pandemic.

“Generally speaking, most vulnerable to pathogen cross-transmission are high-rise, old buildings, those with self-refitted exhaust pipes, fragile water trap seals (U-traps), old and faulty plumbing systems,” Smith said, citing the Hong Kong case above as an example.

While the Hong Kong investigation revealed that pipe repair could have contributed, the culprit is often the U-shaped pipe, called a U-trap that Smith discussed. The U-trap should always contain a small water reservoir that acts as a plug. When it doesn’t, things can get nasty.

“Empty U-traps allow the pathogens to enter households from the sewage system. They transmit freely together with feces and as virus-laden aerosols into the ventilation system. As a final step, they contaminate pipework, toilet bowls, bathroom space, and the extract fan,” Smith said.

In the Hong Kong apartment building’s case, the disconnected vent pipe is suspected to be the issue. It’s thought that if airborne transmission of SARS-COV-2 is playing a meaningful role in the pandemic, then this pipe may have caused aerosolized pathogens to spread through other units.

But can COVID-19 really be spread through contaminated air particles? Scientists have some experimental evidence the answer could be “yes,” but they still consider the odds to be fairly low. They look to the SARS crisis for the answer, and a case that also involved those crucial U-pipes.

In a famously tragic situation in 2009, a Hong Kong complex called Amoy Gardens had ineffective plumbing with dried-up U pipes, resulting in 329 cases of SARS in a single building, 42 of whom died, CNN reports. The event was later referred to by scientists as a “super-spreading” event.

To confirm faulty plumbing is actually the cause of such transmission, researchers conducted experiments in a full-scale pilot test, which concluded four factors really matter when it comes to disease transmission through plumbing, like what happened in the SARS cases:

  • the presence of a depleted U-trap
  • the presence of infectious pathogens within the sanitary plumbing system
  • adequate system airflows to transmit the infectious pathogens
  • the susceptibility of the occupant to those infectious pathogens heightened due to immunity suppression.

The study ultimately concluded that “the experiments prove that pathogens can be transmitted from one part of a building to another on sanitary plumbing system airstreams.”

Despite the evidence from the Hong Kong experiment, it's still up for debate how contagious coronaviruses are through air contamination, especially COVID-19, which seems less so. Popular Science reported that Charles Chiu, associate director of the UCSF Clinical Microbiology Laboratory, said “coronaviruses are not generally airborne. “It’s unlikely that this [new virus] happens to be different,” Chiu says. “It’s more likely that it’s not airborne, although it’s too early to definitely say that yet.”

The bottom line: While we know that coronaviruses can travel through apartment sewage systems, the odds are low of SARS-COV-2 traveling through faulty pipes, then contaminating the air in a bathroom, and then infecting the tenants through inhalation.

Fecal transmission is a worry, but water transmission is not

While the odds of airborne transmission through sewage pipes is low, poop may be a different story. Popular Science reports that “there is some evidence that COVID-19 can be transmitted through contact with infected feces, but scientists don’t know for sure.” Chinese researchers detected RNA from the virus in the stools of people who have been infected.

The CDC confirms that fecal transmission can happen, but the details aren’t concrete: “The amount of virus released from the body (shed) in stool, how long the virus is shed, and whether the virus in stool is infectious are not known.”

Since COVID-19 is mainly transmitted orally, through droplets spread through coughing and sneezing, the poop factor means that there would have to be fecal-oral transmission. This goes back to lesson number one: wash your hands after using the bathroom. If there were disease particles on the toilet seat from an infected person’s feces, it still would have to make it to your mouth, which is impossible if you are thoroughly washing your hands afterward. (This also explains yet another reason that shelter-in-place orders are effective, as you won’t be using potentially contaminated public toilets.)

If for some reason you are in contact with untreated sewage, previous coronaviruses have been detected for up to 14 days in this type of material. So basically don’t touch that.

Americans have concerns, too, about water transmission. The CDC reports that no, you aren’t going to get COVID-19 from a hot tub or pool, because chlorinated and treated water eliminates disease. Workers at wastewater treatment plants are already following the Personal Protective Equipment (PPE) regulations, and therefore don’t have to change anything to further prevent contracting the disease.

The bottom line: The solution for keeping coronavirus out of your pipes is simple, Smith says, and lies in “consistent plumbing maintenance culture.”

“People often find this a chore and overlook the importance of routine plumbing inspections, even if they might be done at minimum cost and time. In pandemic conditions, though, your first step is to ensure that your plumber is wearing protective gear and take personal hygienic precautions in line with the government’s strict measure to contain the virus spreading,” she says. “In times like these, we should not stay idle.”