Published: 13 April 2021

Key Findings

• The presence of chlorine in water, under the right conditions, can inactivate the virus that causes Covid-19 in just 30 seconds.

• Findings follow research by virologists at Imperial College London, led by Professor Wendy Barclay.

• Baby swimming business Water Babies worked collaboratively with Swim England, Spatex Foundation and RLSS UK to provide context and materials for the research.

Swimming pool water can inactivate the Covid-19 virus in just 30 seconds under the right conditions, reveals a study by virologists at Imperial College London, which was commissioned by Water Babies, Spatex Foundation and Swim England.

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.

Founder of Water Babies, Paul Thompson said: “We are excited about these findings as we prepare to restart our classes and plan to welcome back families, little 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 UK 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 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.

The collaborative study 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 in line with current guidance for swimming pool operation.

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

Professor Wendy Barclay, Imperial College, 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, 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.”