Celia's Adventures
in research, zero waste living and discovering the world

Water Conservation - Toilet

Hey hey!

I am back with a new zero waste blog post now as an official Irish Climate Ambassador. As part of the programme, we committed to carry out climate actions and communications throughout the year. I am starting with a new series on water conservation - the first chapter is on toilets! In March 2020 my 3 flatmates and I saved 2025 litres of water in total by not flushing the toilet after every use.

In our shared apartment (after communal deliberation and agreement) we started applying the

If it’s yellow,
let it mellow.
If it’s brown,
flush it down

rule when using the toilet. It is just a simple thing, but we did not know its actual implication.

We were really curious about how much water we actually save with this method, so we decided to track our toilet flushes for a whole month. On a sheet of paper, we simply marked how many times we flushed and how many times we did not (see above).

But actually, March 2020 was kind of exceptional as we were forced to spent half of the month working from home due to the Coronavirus measures, so the data might not be suitable for making the extrapolation for the rest of the year. So, it looks like we’ll need another round of counting when things go back to normal again. Anyhow, I thought it is still interesting to share our estimate…

But let’s get back to the actual numbers. We flushed our toilet 137 times and marked 270 occasions when we did not (but would have in the past without the new rule in place). That means we saved a total of two-thirds of the water that we would ‘normally’ have used for flushing the toilet; really impressive I’d say.

Our toilet uses 7.5 litres of valuable freshwater per flush - yes, we did measure that as well! 7.5 litres by 270 means that we saved 2025 litres of water in the 31 days of monitoring among the four of us. That totals exactly 16.3 litres per person per day. 2025 litres of water is equal to approximately 25 baths (assuming one bath takes 80 litres of water). That is not that bad saving, right?!


Well, now where does that leave us? I wanted to check how this compares to the general water usage estimates in Ireland. According to Irish Water, it is estimated that we use on average 129 litres per day, of which 26% we used for flushing our toilets. So it would mean that people live in Ireland use 36.12 L water per day on average for flushing toilets.

But how you could conserve water using for toilet flushes if the yellow-mellow is not your cup of tea?!

During my research, I also came across an Irish Environmental Protection Agency report titled “Water saving technologies to reduce water consumption and wastewater production in Irish households” written by very talented people I worked with at Trinity College including my PhD supervisor. You can find the link to the report here

According to this report, toilet cistern capacities have decreased from 20 litres in the mid-20th century to 6 or less litres today. It seems toilet cisterns with flush volume around 7-9 litres like ours, were installed between 1993 and 1999. There are also new technologies (dual flush toilet and vacuum toilet with urine diversion) available on the market to reduce the water usage per flush to between 0.6 - 1 litres. Of course, we should not all run to buy a new toilet cistern to reduce our water usage. One super easy solution is just to put a plastic bottle filled with water into your cistern to reduce the amount of water used per flush. And also added a bottle in our cistern to reduce the volume of flushes.

Here you can find further water conservation ideas by Irish Water.

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