Measuring Water Wasted While Brushing Teeth
Last week, a commercial came on TV about conserving water. The person in the ad made the statement that leaving the faucet on while brushing your teeth wastes 5 gallons of water each time you brush your teeth. My daughter asked me if that was accurate. I told her to measure it!
We are also in a severe drought here in North Carolina (I talk more about that at the end of this post. You can also check whether your area of the U.S. is in a drought status and to what degree. There is a link below.)
Procedure
- Find a container to collect water from the faucet.
- Find a timer.
- Find one person to brush their teeth and one to run the timer.
- Start brushing your teeth, leaving the water on after wetting the toothbrush and shut the water off after the teeth are brushed and the teeth and toothbrush are rinsed.
- Be sure to start the timer as soon as the water is turned off and stop the timer when the water is shut off.
- Measure the collected water by pouring it into a container that has measurement lines (if your collection container does not)
- If your collection container is too small to hold all the water follow the following procedure: Time the toothbrushing process. Collect water in a container for 10 seconds and measure the amount collected. Use that measurement to figure out how much water would have been collected in the time it took to brush the teeth.
Results and Ideas for Further Study
We discovered that if my daughter keeps the water running while brushing her teeth, she uses 2.5 gallons. This was half of what the commercial told us. However, dentists tell us to brush a whole 2 minutes and adding rinsing time might bring the expected brushing time up to 2 minutes 20 seconds. My daughter only took 1 minute 30 seconds for the entire brushing process. She used less water, but might not have clean teeth!
Another variable to consider is the faucet. Different faucets have different flow rates. If the flow rate of your faucet is slow, you won’t use as much water in the same amount of time as you would with a higher flow rate faucet.
We took this experiment further.
We decided to capture:
Rinsing method – whether a cup is used or not used to rinse
Different people: Does one family member typically use more water than another when brushing?
Water flow rate: collect water from each faucet for exactly 10 seconds and measure it. This lets students compare faucets even before doing the full brushing experiment.
Projected water savings: use the data to estimate how much water could be saved in one day, one week, one month, or one year by turning the faucet off while brushing.
We have created printable worksheets to help capture, record, and discuss the data.
You can request these datasheets below. This is a good way to learn about:
- The impact of conserving water in your home
- Collecting data and understanding dependent, independent, and control variables
Why Is Water Conservation Important?
The earth’s water cycle does an excellent job in cleaning and processing our water naturally. However, our society uses more water than this process can keep up with.
Our family is on a well system and, unfortunately, right now our state (North Carolina) is in a severe drought. (As of September 2026, we are in the maroon area {extreme drought} just north of Greensboro, NC, on this drought.gov map.) Some of the retention ponds in our neighborhood are days from being almost completely dry. Large lakes in our area are down 70-80% with trees and islands that were once under water in the middle of the lake almost fully showing.
So, for us, this is why water conservation is very important. It could take us years to get back to normal levels. We had a hurricane season with zero tropical depressions or hurricanes. Honestly, we need rain levels that rival a tropical depression to help us out of this extreme drought. We definitely do not need hurricanes, but tropical depressions that bring a slow, steady rain over several days would greatly help our area. NC is an agricultural state.
For households and businesses on city water supplies, conserving water also reduces the amount of water that needs to go to waste water treatment facilities, therefore reducing the amount of energy used and reduces the amount of chemicals put into our water supply.
Looking for more Earth Day activities, check out all of the Earth Day STEM activities here.
