What flies out of a toilet when you flush it with the lid up
Scientists lit up a flushing toilet with green lasers and filmed a plume of tiny droplets shooting 1.5 metres into the air in eight seconds.
In 2022, engineers at the University of Colorado Boulder shone bright green lasers across an ordinary lidless public toilet and filmed what happened when it was flushed. You can find the footage online, and it is hard to forget.
A cloud of tiny water droplets burst upwards out of the bowl at up to two metres a second, reaching about 1.5 metres high within eight seconds. The largest droplets settled within a few seconds, but the smallest, too fine to see, stayed floating in the air for minutes. Earlier studies have found that droplets like these can carry bacteria and viruses from the bowl, and settle on the surfaces around it: the tap, the door handle, the towel, the toothbrush sitting by the sink.
Most home toilets have a lid, and closing it before you flush is the simplest fix there is.
Small bathroom habits that help - Put the lid down before you flush. Make it a family habit, children included. - Keep toothbrushes in a cupboard or as far from the toilet as the bathroom allows, and let them dry upright. - Wipe the flush button, taps and door handles regularly. They are touched by every hand in the house. - Keep the exhaust fan on or a window open for a while after using the bathroom. - When someone at home has a stomach bug, clean the toilet and nearby surfaces daily with a disinfectant.
Where this comes from - Crimaldi JP et al. Commercial toilets emit energetic and rapidly spreading aerosol plumes. Scientific Reports, 2022.
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