Lots of tooth brushing is good

Toothbrushing and Saving Water – A Solution A Day

Background – Human Behavior and Saving Money

Everyday people take various actions throughout their daily routine. Many of these actions start out as choices and turn into a routine. We as a species are creatures of habit. Thus it should come as no surprise that some of these habits can be improved. An example is smoking is a bad habit. Brushing our teeth on the other hand is a good habit. Even good habits can be improved. Today we shall focus on brushing our teeth and how to save water. My family uses Philips Sonicare Toothbrush, brand toothbrushes they are electric rechargeable and effectively clean your teeth. The ones in the photo are the ones we purchased several years ago.

Lots of tooth brushing is good
Tooth Brushes in my house.

The Problem – Water Wasted While Brushing our Teeth

Hopefully you brush your teeth the recommended three minutes twice a day. When you do brush your teeth what do you do? A typical tooth brushing process might be:

  1. Person walks in
  2. Turns on the water
  3. Rinses off the tooth brush
  4. Puts toothpaste on the brush
  5. Brushes for 3 minutes
  6. Rinses off the tooth brush
  7. Rinses out mouth
  8. Turns off the water

While it is difficult to determine exactly how much time the faucet spends running on the average tooth brushing or the average water used (this will vary with length of faucet on and flow rate of the faucet). We can improve the process to save some freshwater, and a small amount of money.

Faucet left with water running
Water left on during teeth brushing

The Solution – Turn the Water Off when not in Use

At my home 100 gallons of water costs 13.77 cents which is not a crazy amount. In fact it is quite cheap compared to say San Diego where they have a tiered system and the cheapest tier 100 gallons costs 48.66 cents and the most expensive tier is $1.0949 for 100 gallons. Let’s make some basic assumptions:

  1. My water rate (which I suspect is on the lower end of the U.S.A.). Compared to the expensive tier for San Diego.
  2. A family of four who all brush their teeth for six minutes per day (two three-minute sessions each person). This amounts to a total of 24 minutes of tooth brushing and the before and after times.
  3. The faucet is only on for a negligible amount of unnecessary time before and after the tooth brushing.
  4. The faucet it either completely on or completely off.
  5. The average flow rate in a residential bathroom is two gallons.
  6. All bathrooms have the same water pressure.

We will change our process to (I’ve bolded the additional steps):

  1. Person walks in
  2. Turns on the water
  3. Rinses off the tooth brush
  4. Turns off water
  5. Puts toothpaste on the brush
  6. Brushes for 3 minutes
  7. Turns on water
  8. Rinses off the tooth brush
  9. Rinses out mouth
  10. Turns off the water


4 (people) * 6 (minutes per day) = 24 minutes

24 minutes * 2 gallons (per minute) = 48 gallons per day

48 gallons (per day) * 365 (days per year) = 17,520 gallons per year

That’s 17,520 gallons per year of water that does down the drain during the three minutes where you are brushing your teeth and not using the water.

17520/100 = 175.20 (hundred gallon charges per year).

Below I multiply the charge by the water rates from above to determine the annual cost.

Dollars wasted at my price per year: $24.132

Dollars wasted at San Diego low price tier per year: $85.2578

Dollars wasted at San Diego high price tier per year: $191.83

Just for fun if the entire American population did this it (assuming all Americans brush teeth)  would save:

Dollars wasted at my price per year: $1,893,762,467.00

Dollars wasted at San Diego low price tier per year: $6,690,602,246.00

Dollars wasted at San Diego high price tier per year: $15,053,855,053.00

Gallons Saved: 1,374,880,000,000


Well most people paying my water rate are probably not terribly inconvenienced by the extra $2 of water each month from this habit. Someone in San Diego might be happy to save $7-15 per month on their water bill. The real important thing here is that today more than ever and as the populations increases, fresh water is very important to conserve especially when we could be using 3.77 billion fewer gallons of water per day (just from turning off the water when we brush our teeth. Let me put this into perspective the flow rate of the Mississippi river (The largest river in the U.S.A.) is only 7.76 billion gallons per day (about twice what we would waste as a country if everyone left the water running while brushing their teeth).