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The Deans of Green

The Deans of Green

Flushing Out the Ultra Water-Efficient Stealth Toilet

comments (10) May 25th, 2010 in Blogs
AlexWilson AlexWilson, contributor

Whats so special about this toilet tank?Click To Enlarge

What's so special about this toilet tank?

A new toilet from Niagara pioneers a radically new flush technology--and uses just half as much water as standard toilets.

Niagara Conservation has introduced a new toilet that's unlike anything on the market. It uses passive "vacuum-assist" technology to deliver a very quiet, effective flush that consumes just 0.8 gallons (3.0 liters)--making it, I believe, the most water-conserving of any flush toilet on the market.

water efficient toilet

Who knew there would be so many ways to flush a toilet!


While pressure-assist toilets use compressed air at the top of a sealed tank to push water through the flush valve at a high velocity (achieving a very effective flush), the vacuum-assist Stealth toilet literally pulls the contents of the toilet bowl down the trapway from below.

Here's how it works:

After the toilet is flushed, water fills a special inner chamber that's hidden inside the conventional-looking toilet tank. (In this respect, it is like a pressure-assist toilet--with its tank-within-a-tank that is filled from the bottom.) As this inner chamber fills, though, air at the top is pushed down through a special transfer tube into the trapway, essentially creating a large air bubble between water in the toilet bowl and water in the sanitary trap near the base of the toilet (see the first diagram). This air bubble, which fills about 12 inches of the trapway, exerts a force on the water in the trapway, raising the water level in the toilet bowl to create a larger water spot (water surface area) than would be expected from a toilet using just 0.8 gallons per flush.

image of stealth toilet

When the toilet is flushed, water exiting the inner chamber creates a vacuum--depressurizing the trapway. This depressurization creates a suction force that pulls water from the toilet bowl into the trapway. During the flush, the trapway is entirely filled with water, which cleans the fully glazed trapway.

The vacuum-assist flush mechanism helps the toilet effectively flush a significant quantity of waste using very little water. Using the now-industry-standard Maximum-Performance (MaP) testing protocol, the Stealth toilet is rated at 600 grams, in both the round-front and elongated-front models. This and other performance features have allowed the toilet to earn the EPA WaterSense label for high-efficiency toilets. According to Cecilia Hayward, the marketing manager at Niagara, the toilet also passes all IAPMO requirements for toilets, including a requirement that waste be effectively moved 40 feet along the drainline when the toilet is flushed.

Pressure-assist toilets are popular, because the extra force on the flush does an excellent job at evacuating the toilet bowl and waste in it, and some of these toilets do so with just 1.0 gpf. But pressure-assist toilets are louder than gravity-flush toilets, producing a characteristic "whoosh" during the flush. To an unsuspecting user, they can be quite startling.

The vacuum-assist mechanism in the (aptly named) Stealth toilet avoids that noise. According to Bill Gauley, P.Eng., principal of Veritec Consulting in Mississauga, Ontario (and the co-developer of the MaP testing protocol for toilets), "it is no louder than any other gravity-flush toilet--and much quieter than a pressure-assist toilet."

According to Chris Hanson, who is president of AquaPro Solutions, a water products distribution company and director of the Aqua Environmental Resource Center, both in Ashville, North Carolina, the toilet performs even better in his own MaP tests--consistently removing 800 grams of test media. He has one of the toilets that he's been testing off-and-on for about eight months, and the toilet has also been installed some of that time in the Resource Center--where it has worked without incident. He told me that it's not only quieter than pressure-assist toilets, but also quieter than most gravity-flush toilets, including Niagara's own Flapperless toilet.

One issue to be aware of, according to Hanson, is that because so little water is used for the flush (half the federal maximum), waste may not be conveyed as far as with toilets that have higher flush-volume. He suggests installations where the "horizontal run" will be no more than about 20 feet, before reaching a vertical stack.

Regarding waste conveyance, Gauley said, "I would not be concerned installing this toilet in any residential situation, though I would not recommend it at this time in non-residential installations."

The Niagara Stealth toilet was first introduced in a soft launch in the fall of 2009, but the formal launch was at the Kitchen & Bath Industry Show (KBIS) in April 2009.

The Stealth carries a manufacturer's suggested list price of $310 in the round-front model and $325 in the elongated front model. The product is proving popular, according to Hayward, who estimates that up to 1,000 have already been sold.

In the U.S. Niagara is the exclusive manufacturer of toilets using this technology, while in Canada the same mechanism is used in Proficiency toilets made by Hennessy & Hinchcliffe (the company that invented the Stealth flush technology as well as Niagara's Flapperless technology). Hennessy & Hinchliffe and Niagara are business partners and collaborated on incorporating the Stealth technology into marketable toilets.

For more information:

Niagara Conservation Corporation
Cedar Knolls, New Jersey
800-831-8383, 973-829-0800

Hennely & Hinchcliffe
Woodbridge, Ontario
800-668-4420, 905-850-8080

I invite you to share comments on this blog. Any experience with this toilet?

Alex Wilson is the executive editor of Environmental Building News and founder of BuildingGreen, LLC. To keep up with his latest articles and musings, you can follow him on Twitter.

posted in: Blogs, bathroom, plumbing, toilet, vacuum-assist, water efficiency, conservation
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Comments (10)

LisaPegg LisaPegg writes: We bought a house Nov 2015 with one of these toilets installed... It was working fine but now it is emptying and refilling about every 10-15 mins and my water bill has skyrocketed! I can't figure out how to fix it... I have searched and searched online but can't find any solutions to fix it...can anyone out there help me?
Posted: 3:42 pm on March 26th

Toileteer Toileteer writes: I would just add, that is on a cast-iron drain 60 years old, 10-11 feet from the stack. Velocity is important as well as volume and I think the velocity helps 'move things along' with this product. Once the waste is in your stack, all the other water use in the house helps move it to the street. I have had no problems.
Posted: 7:56 am on May 1st

Toileteer Toileteer writes: I have been testing one of these for a year. Absolutely wonderful flush, fast refill, quiet and very stylish design, comfortable toilet. Only one tiny snag, if you pour a bucket of mop water down the toilet, you should flush as well, or the back pressure from the water poured down the bowl somehow makes the mechanism leak a small amount and the toilet will pulse a bit, until you flush. Flushing always clears the problem and only uses 3L of water. In one year of operation I think I have had to double flush this toilet only once for normal use!

I am seriously thinking of installing this unit in my apartments because there are no user-serviceable parts for tenants to abuse, the whole mechanism is sort of under cover inside the tank. So I would save water and superintendant bills. A contractor version of the same toilet has been in my mother's apartment in Toronto for a few years and it works great. The unit I ordered for my house is a lot beefier construction when you look in the tanks and the flush button feels more definitive than the contractor version or earlier version that I saw elsewhere.

A lot of readers seem to be missing the point, demanding in the wall units and a two-volume flush. This toilet works great with a single flush volume that saves as much water every time as the smaller 'liquid waste' volume in a lot of other toilets, and has more velocity behind the flush than you might expect. As far as in the wall, I suspect that the exact shape of the passages from tank to bowl and the proximity are important to the operation and it might take some development buy why complain about such a great product that could replace 99% of existing toilets?

Posted: 7:35 am on May 1st

montani1970 montani1970 writes: @ lash66

Head over to to see their entire product line of wall-mounted toilets. Great stuff. sells them at a pretty good price.

Though I'd like to see this technology in a wall-mounted unit ASAP!
Posted: 8:56 am on June 6th

lash66 lash66 writes: When will we see these advances combined with the European style of putting the tank in the wall, hanging the bowl from the wall, off the floor (much easier to clean),and having two flush volume selections?
Posted: 7:47 am on June 6th

Mike_Guertin Mike_Guertin writes:
It's been almost a week since I installed a Stealth toilet. It works better than the 1997 1.6 gallon it replaced. The flush is fast, not noisy, and the recovery rate is - well, half the time.

The water spot is larger and deeper than the old toilet and better than I expected.

You don't appreciate the engineering that Alex describes until you push the button on top. It flushes, the bowl clears and the water spot fills all in an instant.

Part of the flush/refill water cascades from under the rim and seems to wash at an angle rather than straight down. I think this helps give water more 'hang time' on the 'above the waterline' portion of the bowl helping to clean it.

One neat thing about the ultra low flush is that the tank has plenty of reserve capacity inside for back-to-back full flushes if needed. We haven't needed yet though; but should the need arise.

We'll see how the flush mechanism holds up. I have high hopes for it. So far it has solved one problem of the original toilet - flapper chain hang-ups.

The configuration of my drains are probably worst-case for an ultra-low-flow toilet. 20 ft. run at 1/8 in. per foot on one pipe diameter upsize from from fixture load requirement. At 20 ft, there's a 90, a 45 into a TY and on to a 20 foot pipe to the septic tank. That run is 1/4 per foot. I scoped the cleanout yesterday and there's nothing lingering on the low slope run.

I'll bet there are a lot of desert southwest municipal water conservation managers eying the Stealth for their toilet replacement programs. Who knows, they may be replacing tens of thousands of 1.6 gpf models they only installed a few years ago.

Posted: 2:52 pm on May 29th

mikeymo mikeymo writes: I may go for it, just based on the larger waterspot. I have a Sterling dual flush upstairs now, and it does an amazing job, clearing 95% of #2s while using just the #1 flush, which is .8 gallons. But it has a tiny waterspot, which allows for a certain earthy smell that not everybody is so crazy about, especially if you're trying to get through War and Peace while in the seated position. If it pays for itself in 5 years, all the better.
Posted: 11:37 am on May 28th

Mike76 Mike76 writes: I have a hang-up with water saving toilets. They may get the contents out of the bowl just fine but what happens down stream in your plumbing pipes. I can guarantee that your average residential building drain + building sewer are longer in length than 40 feet by the time they get to the city sewer pipe. Compounding this is the fact that most older homes have cast iron soil pipe which is notorious for plugging up. The idea of this toilet may make you feel all warm and cozy in side until you have to call a drain cleaner for $300.

Posted: 9:41 pm on May 27th

kelt0004 kelt0004 writes: This would certainly be worth it if replacing an older toilet.

The average american, according to multiple sources, flushes 5 times a day. Multiply that by the number of days in the year (365) and the number of people in an average household (3.2) that equals 5840 flushes a year. As, older toilets may flush as inefficiently as 3.5 gpf, this toilet could save some 15,768 gallons per year. Of course, figure that for a 10 year life and you've just saved 150k gallons. In my area, that is a cost savings of about $600.
Posted: 1:04 pm on May 27th

ChadC ChadC writes: The price isn't bad, but the water savings isn't significant for residential use. A gravity flush toilet would only use 1L or so more per flush, and that would only be a few liters per day at my house. I can see how this would be nice for commercial use, but it's not recommended for that?

Wouldn't be worth trading in a 900 gram gravity toilet for a 600 gram assisted flush, not for 1L.
Posted: 11:59 am on May 27th

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