Should you close the toilet lid before flushing? What two studies found

In many homes it's the rule: lid down, then flush. The habit got a boost in 2022 when engineers at the University of Colorado Boulder used green lasers to film what happens when a toilet is flushed. Within eight seconds, tiny droplets had risen about 1.5 metres into the air.

But a 2024 study published in the American Journal of Infection Control came to a less obvious conclusion. Researchers added a harmless test virus to toilets, flushed them with the lid up and down, and checked nearby surfaces. Closing the lid made little difference to how much virus was found. What mattered more was cleaning.

With World Toilet Day on 19 November, it's worth looking at what these findings mean for your bathroom.

What the lasers revealed

The 2022 experiment, led by engineer John Crimaldi at the University of Colorado Boulder, made the invisible spray from a flush visible. Using green lasers and cameras, the team filmed tiny droplets travelling upwards at speeds of around two metres per second. They reached about 1.5 metres above the bowl within eight seconds. You can see the footage in this Medical Xpress report.

However, the researchers used clean water and studied how droplets moved, not whether they carried germs. They also used a commercial toilet without a lid, so the experiment didn't establish whether closing a household toilet lid helps.

What the virus study found

The 2024 researchers added a harmless virus called MS2 to household and public toilets. After flushing with the lid both up and down, they checked how much had reached nearby surfaces.

There was no significant difference in the amount of virus found between the two methods. Closing the lid changed where some contamination landed, but didn't prevent it from spreading.

Cleaning made a much bigger difference. Using a toilet brush together with disinfectant reduced the virus in the bowl water by more than 99.99 percent. The amount found on the brush was also 97.64 percent lower than when brushing without disinfectant.

So, should you put the lid down?

Yes, if your toilet has one. It's a simple precaution, but the lid doesn't create an airtight seal. Tiny droplets can still escape through the gaps around the seat and bowl. So don't treat closing it as a replacement for cleaning.

A simple routine for a cleaner toilet

For everyday cleaning, the Dutch RIVM says ordinary household cleaning is generally enough. Disinfectant isn't usually necessary in a healthy household.

If someone at home has a stomach bug, extra care is sensible. The RIVM's norovirus advice recommends:

• Flush with the lid closed.
• Clean the toilet regularly, including the seat, flush button and surrounding surfaces.
• Use a separate cloth for the toilet.
• Change the bathroom hand towel daily.
• Wear disposable gloves and use disinfectant when cleaning up vomit or diarrhoea, following the product instructions.

World Toilet Day takes place on 19 November. The 2026 theme is sanitation and gender equality, with the slogan “Safe toilets. Equal futures.” At home, the takeaway is simple: put the lid down if you can, but remember that regular cleaning and good handwashing habits matter much more.