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.
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.
Click the image for a detailed diagram showing how how the Stealth toilet works.
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
Hennessy & Hinchcliffe
See more on this product in the
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 sign up for his Twitter feeds
Top photo: Niagara Stealth toilet
Graphic (middle): Stealth flush mechanism schematic
Bottom photo: Flush mechanism shown in transparent housing
All images: Niagara Conservation Corp.