December 15 2007

Waterless Urinals - How do they work?

Waterlesss Urinals_Image 01I am fascinated by waterless urinals. The very notion that a ammonia and nitrogen filled bodily fluid can be disposed of by a device using no flushing or running water is truly amazing to me. After doing a little reading into the science behind the products I am now even more impressed at the simple genius behind the waterless urinal!

Waterless urinals all use basically the same science. Urine flows down the bowl of the urinal past a debris-catching strainer. The urine then passes through a sealing liquid, usually a specially designed oil based fluid or simply vegetable oil, and collects in the waste pipe below. The different densities of urine and oil (urine is denser than oil - oil floats!) mean that the urine sinks through the sealing liquid and the oil floats on top of the layer of urine below. Any air bubbles rise to the top and escape leaving the urine in a relatively low oxygen environment. Odor is therefore trapped below the oil layer and cannot find the nose of bathroom occupants.

Densities of the liquids involved are:

    • 823 kg/m3 - Ammonia
    • 920 kg/m3 - Oil
    • 1021 kg/m3 - Water

It is important that the urine is slowed sufficiently before it hits the oil so that laminar flow displacement doesn't move the oil to the bottom of the waste pipe. If the urine is slowed sufficiently this is not a problem. After the urine is in the waste pipe it is a simple matter of displacement that sends the urine into the regular plumbing system, it is recommended to call plumber ipswich to give maintenance to the drain system.

There are two varieties of waterless urinal: cartridge based and non cartridge based units. Cartridge based units use a replaceable cartridge pre-filled with sealing liquid. These units are periodically replaced as the sealing liquid is slowly eroded or degraded. Non Cartridge based systems work by simply introducing the sealing liquid into the drain hole and allowing it to naturally settle into the correct position.

Waterless urinals were introduced to the world by the Waterless Company in 1992. The first urinal used what was called an EcoTrap cartridge. Others manufacturers which started producing them almost a decade later include: Falcon Waterfree Technologies, Sloan Valve Company, Duravit, Kohler and many others.

Waterless urinals are also becoming increasingly popular as the green building movement takes hold with certification programs such as LEED. Two major barriers that once stood as impediments to the adoption of waterless urinals, regulatory and facility managers, are being gradually eroded through education on the benefits, safety and easy maintenance of the urinals.

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January 16th, 2008 at 1:20 PM

Greenline » "Smart" Urinal?

[...] The Australian plumbing products company already sold a waterless urinal model.  (See our previous post on the technology.)  They also sold a standard low-water use model.  The new product is intended to fit the [...]

March 9th, 2008 at 12:32 PM

Andrea Paulinelli

The Caroma H2Zero Cube Urinal transforms the way you think about waterless urinals and heralds a major breakthrough in waterless technology. This product is the first truly viable and sustainable high performance waterless option. For more info on Caroma Products, please visit EcoTransitions' or Caroma USA website. Best regards, Andrea Paulinelli

May 26th, 2008 at 5:19 PM


without water flushing and cleaning the wall of the urina won't that be dirty and stained?

June 2nd, 2008 at 12:17 PM


Just a quick follow up to "Curious": Proper maintenance of a waterless urinal (and for that matter, ANY urinal) requires a regular wipe-down/cleaning of the urinal wall. This may need to be done more frequently than a standard model, but with no flushing water running down the wall, there are also no hard water or rust deposits to clean. So long as maintenance staff is trained properly, there shouldn't be any issues with smell or cleanliness of the porcelain.

July 7th, 2008 at 9:50 PM

Waterless urinals « Absent-Minded Jay

[...] out an article on waterless urinals. Goodbye and Good [...]

July 26th, 2008 at 3:50 PM


According to your listing of liquid densities, ammonia is less dense than oil, therefore it will float on top of the oil. since ammonia is very volital, it will stink up the joint!

March 31st, 2009 at 10:12 PM

DNW Resources

ZeroFlush waterless urinals are the way to go. With the biggest trap design in the industry and lower priced consumables, you will save a lot more money. Save money, save water, save the environment and many other benefits. It's a simple decision. Get ZeroFlush and start your savings ASAP.

April 11th, 2009 at 12:23 AM


What happens at the processing plants? With undiluted sewage, does it take more water, cleaning, cost?

June 2nd, 2009 at 1:40 PM

Sustainability in the Lavatory « big green buildings

[...] Waterless urinals use a sealing liquid?typically an oil, which is less dense than urine?that lets urine flow through and sink beneath. The oil traps any odor. There are two types of waterless urinals, one that uses a cartridge, which encases the sealing liquid, and non-cartridge systems, which put the sealing liquid directly into the drain hole. Waterless urinals don?t need piping, flush controls, or sensors. They greatly reduce maintenance and installation costs. [...]

June 2nd, 2009 at 1:44 PM

big green buildings

Just wanted to say that I appreciated your info--found it useful in putting together an overview of technologies to conserve water in the lavatory. Not the most appealing subject, but a lot of water can be spared from going down the drain in the washroom!

June 28th, 2010 at 8:32 AM


I saw one in McDonald's - it said that this one urinal saves 100,000 litres of water annually. that has GOT to be worth a few additional maintenance visits Good work on a great article, BTW!

January 8th, 2011 at 10:29 PM


Doesn't this mean that you could just take a regular urinal, disconnect the water supply, pour some vegetable oil in it, and it would work perfectly like a waterless urinal?