How long does a shower have to be, to use the same amount of water as a bath?

Asked by: Lawrence Berry, by email

A bath filled about a third of the way up (which takes the water level over your belly button when you lie down) requires around 75 litres. An ordinary electrically heated shower puts out four litres per minute. So a 19-minute shower is just more than a bath. If you have a power shower, flow rates could be doubled and you’d need just 10 minutes.

Read more:

• How often should you wash your bath towels?
• Which is less green: soap or shower gel?

Subscribe to BBC Focus magazine for fascinating new Q&As every month and follow @sciencefocusQA on Twitter for your daily dose of fun science facts.