Tip 001 — Use a glass when brushing your teeth

This is the very first of many sustainability tips and challenges that I’m planning to share with you — and because it’s the first, we’ll start nice and easy.

For my Portuguese folks out here, I have a musical introduction:

Anyone else remembers learning this in elementary school?

The lyrics say:

A glass of water, a toothbrush and toothpaste,
To wash my teeth is all I need.

The glass of water is the star of this tip. While most of us already close the tap while we’re brushing our teeth (if you don’t, that’s Tip 000 for you), this little trick can help us save 1l (or 0.26 gallons) of water or even more each time we brush our teeth.

Disclaimer: the values used on this post are based on averages and estimates, therefore they will be different depending on a number of things. That being said, 1l (0.26gal) of water is a very modest estimation because a lot of people easily use over 2-3l (0.5-0.8gal). If you want to know how much water you would be saving by doing this, the best way is to measure your own values, which I tell you how to do below.

How does it work?

You start by filling half a glass with water, and that’s the only time you open the tap during this teeth brushing process. Dip the toothbrush on the cup to get it wet, then put on the toothpaste and brush your teeth normally. Once you’re done, clean the toothbrush using the water from the cup. If you normally rinse your mouth after brushing,[7] use half the water for it before cleaning the toothbrush.

Easy peasy, yes?

Let’s talk numbers

Assuming that:

  1. We brush our teeth 2x per day;
  2. We use a little over 1l of water when brushing our teeth “normally” and only 100ml when using the “glass” technique;

This would represent saving of 2l of water every day.

per month60l
(15.9 gal)
per year730l
(192.8 gal)
long-term (30 years)21,900l
(5,785 gal)

Initial investment: €0.00

* Based on Coimbra’s water price.[1]
** CO2eq means CO2 equivalent. It’s a unit of measurement used to standardise and compare the climate effects of greenhouse gases based on their global warming potential (by converting its amounts to the amount of carbon dioxide that would have the equivalent global warming potential).[2]
While its purpose is the comparison of greenhouse gases, it is possible to reach an estimate for water usage based on the energy required to pump, transport, treat and desalinise said water.[3]

How much is 730l of water worth?

Amount of water required to produce different kinds of food (listed in text).

It is roughly the average amount of water required for the production[4] of either one of the following foods:

  • 42g (1.5oz) of chocolate
  • 300g (10.5oz) of rice
  • 1kg (2.2lb) of bananas
  • 2kg (4.4lb) of pumpkins or cucumbers
  • 3kg (6.6lb) of cabbage or lettuce

So I guess the question is…

Would you throw 1kg of bananas down the drain?

Next time you use a glass while brushing your teeth, think about the number of bananas you’re saving each year!

Additionally, the United Nations tells us that each person in Portugal spends on average 187l of water each day, so, to the average Portuguese, this could represent a 1% reduction on water usage.[5] At the same time, the World Health Organization (WHO) tells us that a human being needs between 50 and 100l of water each day to meet the most basic needs,[6] which means you could save from 7 to 15 days worth of water every year!

How to calculate your own values

If you’re suspicious these calculations don’t apply to you, you’re probably right. As I mentioned earlier, these numbers are based on averages and estimates, however, what you can know for sure is how much water you’d save by following this tip.

Simply brush your teeth as you normally do but collect the water and weight how much you spent. Then subtract 100ml (or 0.026gal), which is roughly half a cup of water.

That’s the amount of water you’re saving every time you brush your teeth!

Additional quest

Are you using too much toothpaste?
Although many people cover the top of the bristles with toothpaste as we see in commercials, in reality, we only need to use a pea-sized amount (or rice-sized, for kids under 3).[7] Consider adjusting the amount of toothpaste you use for additional resources (and money!) savings.

The end

Tell me, do you already do this? If you don’t, will you give it a try? And if you do, will you convince someone else to do the same? 😃

Let me know what you think of the information I shared here, if I missed something, or if you have any questions and curiosities! Leave a comment below.

See you soon!

  1. Coimbra water prices
  2. CO2 Equivalent
  3. CO2eq of water
  4. The water footprint of different foods
  5. Water usage
  6. Water needs
  7. Oral hygiene needs
  8. Icons