Swimming pool water inactivates Covid-19 virus in 30 seconds, new study finds

Swimming pool water can inactivate the Covid-19 virus in just 30 seconds under the right conditions, a study by virologists at Imperial College London has revealed.

The findings, which have not been published in a peer-reviewed journal, suggest the risk of transmission of Covid-19 in swimming pool water is incredibly low, as indoor swimming pools and leisure centres reopen across England on 12 April as part of the government’s roadmap to ease lockdown restrictions.

The collaborative study, commissioned by Water Babies and Swim England, looked at the effects of swimming pool water on the virus that causes Covid-19, named SARS-CoV-2, to assess the amount of time and contact needed to inactivate the virus in varying chlorine and pH levels.

The research established that 1.5mg per litre of free chlorine with a pH between 7-7.2 reduced the infectivity of the virus by more than 1000 fold within 30 seconds. Additional testing of different free chlorine and pH ranges confirmed that chlorine in swimming pool water was more effective with a lower pH. This is inline with current guidance for swimming pool operation.

The study into swimming pool water was undertaken by leading virologist and expert in respiratory viruses, Professor Wendy Barclay, together with research associate Dr Jonathan Brown and research technician Maya Moshe from Imperial College London and project managed by Alex Blackwell, Head of Pools and Facilities from Water Babies.

Professor Wendy Barclay explained: “We performed these experiments at our high containment laboratories in London. Under these safe conditions we are able to measure the ability of the virus to infect cells, which is the first step in its transmission. By mixing the virus with swimming pool water that was delivered to us by the Water Babies team, we could show that the virus does not survive in swimming pool water: it was no longer infectious. That, coupled with the huge dilution factor of virus that might find its way into a swimming pool from an infected person, suggests the chance of contracting Covid-19 from swimming pool water is negligible.”

Paul Thompson, founder of Water Babies, said: “We are excited about these findings as we prepare to restart our classes and plan to welcome back families, littles ones and customers to indoor swimming pools across the country. It has been fantastic to work closely with Professor Barclay and her team at Imperial College and collaborate with leading bodies Swim England and RLSS on this world-leading research. We know swimming has multiple benefits for physical and mental health for both children and adults of all ages and we’re looking forward to our lessons restarting.”

The research was also supported by Swim England, the national governing body for swimming in England and the Royal Life Saving Society, the UK’s leading provider of water safety and drowning prevention education.

Jane Nickerson, Swim England chief executive, said: We’re delighted to have played a key role alongside Imperial College London, Water Babies and RLSS UK in this world-first piece of research.

“These findings suggest the risk of transmission from swimming pool water is low, and adds to the evidence that swimming pools can be safe and secure environments if appropriate measures are taken.

“As indoor pools were allowed to reopen on Monday 12 April, it’s fantastic news for the operators, our members and clubs who take part in all our amazing sports, recreational swimmers and those who rely on the water to stay physically active.

“The findings confirm the guidance we have issued to operators is correct and will give everyone returning to the water peace of mind that they are doing so safely.”

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