You have to be aware of all the possible risks when you have a virus that is rapidly spreading and has a high rate of transmission.

Tower blocks and hospitals are large buildings that have not received any attention. Our research shows that while direct transmission from person to person is the most common way of getting the disease, occupants of tall buildings may become infected by plumbing defects. People should be aware of the dangers and take precautions to protect themselves.

The Institute for Sustainable Building Design, Heriot-Watt University, was inspired by a 2003 outbreak in an apartment building in Hong Kong called Amoy Gardens. In a building with a total of 19,000 residents and a height ranging between 33 and 41 floors, over 300 cases were confirmed, and 42 people died – about one-sixth of all SARS deaths and infections on the island.

The World Health Organization report on the SARS outbreak suggested that the primary cause was defects in the wastewater drainage at Amoy Gardens. The U-bends that normally contain water in toilets and sinks to prevent airborne disease from rising from the sewer system were dry in the bathrooms of Amoy Gardens.

Amoy Gardens, Hong Kong. Wikimedia

According to the WHO report, when SARS-infected people had diarrhea in the toilets of the building, “airborne virus-laden droplets”, could travel via the sewer network and plumbing system from one apartment. The airborne route of transmission was made easier by bathroom extractor fans that drew in contaminated air.

Our work

Our group has been researching the cross-transmissions of infections in buildings since nearly 20 years. In 2017, I, along with David Kelly and Thomas Aspray (my co-researchers), published the results of an experiment conducted on a two-story full-scale wastewater plumbing test rig. We used a model to represent pathogens that were flushed through the system while creating the same type of defective conditions found in the Hong Kong block.

This proved that these organisms could be spread between rooms in a building on different floors by the airflow system, which helps the water move around the plumbing. The microorganisms were not only in the air of the rooms but also on surfaces and in the plumbing system.

In our article, published in PLoS, we noted that the wastewater plumbing systems of large buildings were connected in all areas. U-bends that are not dry allow contaminated air to enter and exit the space freely freely. These buildings are more susceptible to pressure surges caused by overuse, especially when there are many people at home. This can cause water to leak out of U-bends and damage their seal. The dry U-bends at Amoy Gardens were partly due to this.

COVID-19 has far-reaching implications. The virus is spread through air droplets. Diarrhea is not one of the most common symptoms, but there are many.

In large buildings, U-bends are especially vulnerable to having their water seals blown out by the pressure from more people using the system at once than normal. Or in hospitals due to overcrowding. In fact, the same risks can be posed by water evaporating from U-bends due to under-use of plumbing – in lockdown, there may still be sinks and bathroom floor drains left in flats.

Keeping U Safe. VDB Photos

A high concentration of diarrhoea-infected people can increase the viral load, increasing the risk of spreading the disease around the building. The interconnectedness between such plumbing systems can also facilitate the spread of infection to nearby buildings. This is a concern for places where there are many infected individuals, like hospitals and healthcare buildings.

Staying Safe

What can we do about it? Recently, we published a Lancet Global Health article that included six suggestions for facility managers and homeowners to ensure their systems remain safe during lockdown.

Don’t ignore foul smells that are not explained in the bathroom, kitchen, or laundry area.

Be sure that all toilets and sinks are equipped with a U-bend.

In the morning and at night, pour water into every sink and toilet for at least 5 seconds. Pay special attention to the floor drains of bathrooms and wet areas.

Seal the pipe immediately if it appears that the waste water pipes from a sink, toilet, or other household appliances are disconnected or unplugged. You can use rubber gloves to seal the end, or you can use a plastic bag with some tape.

Seal any leaks or cracks in the pipework with strong tape.

The building’s performance should be monitored continuously, including drainage issues and bad smells.

On a longer-term basis, it is important to have proper procedures in place that ensure wastewater plumbing systems are designed, keeping infection control in the forefront. There are no codes that govern the design of drainage systems in buildings with more than 50 floors. Some of these design methods date back to the mid-20th century, while others are from the Victorian era when buildings weren’t as tall as they are today. Once the pandemic is over, these things must be redesigned as a priority.