If It’s Yellow Let It Mellow: The Great Debate

by Jordan Laio, Networx

The topic of letting urine sit in the toilet until a number two comes along (known widely by the euphonic expression, “If it’s yellow let it mellow, if it’s brown flush it down…”) can cause quite an emotional reaction in people. Especially when this approach is applied in a household with disagreeable family members or guests. Many would say the very thought is disgusting.

Some people, upon seeing something distasteful in the toilet bowl before they use it, will actually pre-flush before they evacuate their own waste into the bowl, presumably because they want their own waste to have a full bowl of clean water all to itself.

I realize that this is one of those topics where it’s near impossible to convert anyone, in which case I’m preaching to the choir. Well, so be it, because it needs to be said.

The Water We Waste

What is truly disgusting is how our current human waste disposal system works in the United States. We take about 1.6 gallons of good drinking water to flush 10 ounces of urine and toilet paper down the toilet. In doing so, the 1.6 gallons become undrinkable.

Next, the water must be routed to a wastewater cleaning facility where it is processed, usually with heavy chemicals like chlorine, then processed once more to remove the chemicals that were used to decontaminate it. Then it is dumped into the rivers and oceans. In other words, we take perfectly good drinking water, make it toxic and then doubly toxic, clean it and then dump it into the environment.

In reaction to this massive waste of drinking water, countries like Singapore have created wastewater treatment facilities that clean wastewater effectively enough that it is considered safe to drink. Such facilities supply about 30 percent of Singapore’s drinking water.

Let It Mellow

But there are much simpler courses of action, which brings us back to “If it’s yellow, let it mellow.” This technique is so simple and yet effective at conserving water. The average person urinates about 6 times per day, equal to 7.6 gallons flushed. That’s about 2,774 gallons per year to dispose of about 171 gallons of urine. On the other hand, the average person defecates about once per day. If that was the only occasion on which a person flushed, that equals about 584 gallons flushed, saving 2,190 gallons of drinking water. In a household of four, that would be 8,760 gallons saved per year.

What Are the Downsides

There is the irrational aversion many people have to looking at urine. Then there is the more serious concern about toilet bowl cleanliness. True, “letting it mellow” increases the rate at which a toilet bowl becomes scummy. However, in many households, the toilets are brushed at least once a week (hopefully) anyway, and so there is no chance for significant scum to build up.

What Else Can I Do With My Urine?

There are also waterless toilets, which will save water but can be expensive. Composting toilets are also an option.  If you really want to get creative, urine is filled with nitrogen and can make an excellent garden supplement. It is also supposedly effective at repelling deer from private farms and gardens.

Image: Steakpinball / Flickr

Water Saving Tips for Your Toilet
25 Things You Might Not Know About Water
Regular vs. Recycled Toilet Paper


Janet B.
Janet Babout a year ago


Laudia Price
Laudia Price1 years ago

Maybe I could try turning my urine into water again.

Jo S.
Jo S2 years ago

Thank you.

Jo Recovering
Jo S2 years ago

Thank you.

Jo S.
Jo S2 years ago

Thank you for the info.

Morrigna Pavietre

We do this! I do it for water saving reasons. My boyfriend doesn't share my concerns but at least he is not bugging me to flush after myself haha

ERIKA S3 years ago

thank you

Ganaisha Calvin
Ganaisha Calvin4 years ago

the smell can be aversive too. some people have really strong pee.

Christina B.
Christina B4 years ago

Ι am pleasantly surprised to read such an article in Care2. The technique described is not new to my household, however I must point out this: in Greece, toilet paper is not flushed, because our sewer system can't support it. We use a wastebasket instead, where the used paper is disposed. Unless a similar system is employed in the US, I don't see how you can have a toilet bowl full of used paper that doesn't clog up every day.

Bryna Pizzo
Bryna Pizzo4 years ago

Thank you for the information. I neither thought about this nor heard the phrase before today. We will try it, but I plan to keep a box of baking soda in all of the bathrooms.