When I first read 8 gallons of water I thought that sounded like a lot, but according to multiple websites an average household bathroom faucet flows at a rate of 2 gallons per minute. It's a fairly standard dentist recommendation that you brush your teeth for two minutes, two times a day. So with that little bit of math, we would each use approximately 8 gallons of water a day if we left the faucet running while brushing our teeth! That's a lot of water!
If you already turn the faucet off while brushing then pat yourself on the back, give yourself a gold star, and know you're saving almost 3,000 gallons of water every year! A seemingly little step that really adds up! If this is something you could improve upon, then start the next time you brush.