Here’s Todd in his own words:
WOW!!!!

I can not believe the efficiency of this thing. Try as we might we have not been able to get it to clog or not fully flush even with the .9 gallon flush. Read more: DIY Installation and performance of Low Flush Toilet.

There are several aftermarket retrofit kits available today that promise to transform a standard toilet into a dual flush model that can “save more water than a high priced high-efficiency toilet.”

Unfortunately, these gadgets simply regulate the amount of water entering the bowl and do nothing to alter the water flow in or out of the bowl.  Since bowl design is the most important factor in a toilet’s performance – and even more critical in low-flow toilets – these kits promise far more than they deliver.

As the Professor has previously explained, standard and dual flush toilets have different flushing mechanics.  While standard toilets depend on siphonic action to “pull” waste out of the bowl, dual flush toilets rely on the “push” of water to clear the bowl.  More advanced technology, such as the WaterSense-certified H2Option Dual Flush Toilet, combines the traditional siphonic “pull” force with the newer “push” action associated with the washdown flush.

Because standard toilet bowls are not specifically engineered for less water, homeowners will have as much luck using these retrofit kits as they would adding a brick to the toilet tank.  Both strategies try to “trick” toilet science and will likely result in incomplete flushes.  Worse, users will likely overcome this problem by – you guessed it – flushing again.  Multiple flushes eliminate any possible water savings.

In addition to voiding the American Standard warranty on toilets, installing these types of gadgets will frustrate homeowners and discourage any future use of proven water saving technologies such as HETs and dual flush toilets.

Physics, as it turns out, is it right up there with “can’t fool Mother Nature.”

Coined “Drain Line Carry,” the ASME Standard requires that every toilet – regardless of water volume used in a flush – be able to drive 100 ¾-inch polypro balls down a 3-inch rigid pipe an average of 40 feet.  All of American Standard’s water closets meet this standard and many, including Champion 4, Cadet 3, Colony FitRight, Evolution2 and H2Option, exceed that requirement by more than 16 feet. Here’s where we test:

Helping to transport waste through drain lines is what engineers term “supplemental flow,” or additional water generated from faucets, showers, clothes washing, etc., which is obviously more prevalent in residential than commercial applications.

In other words, drain line clogging isn’t likely to be caused by a water saving toilet. Other common causes of drain line clogging are broken or misaligned pipes, buildup of grease or grit within the drain, as well as flushing inappropriate materials.

Special note to commercial building professionals: Installations with extremely long drain lines (e.g., shopping malls or industrial sites), may require evaluation on a site-by-site basis, especially if no supplemental flows are available.

Glenn Hasek of Green Lodging News, notes the downside to some models regarding the small area of water in the bowl also known as the water spot:

“…some dual flush toilets do not clean the bowl as efficiently as traditional single-flush versions. Be sure to ask vendors about this. Without getting into too much detail here, you obviously do not want to leave your guests with a bad impression and you do not want to add to the work load of your housekeepers.”

Hasek echoes what the Professor has said before about dual flush toilets.  “Dual flush toilets that use a siphonic design have a water spot the size found in standard toilets.“  Learn more from Toilet Scientist Jim McHale and follow Hasek’s blog at Green Lodging News:

H2Option

H2Option is the first truly siphonic dual flush toilet, with strong push and pull action created by forceful but quiet jetted action under the rim.

Why does that matter?   As we learned earlier in Flushology, dual flush  toilets do a great job of saving water, and many work great at the toilet’s most important function–getting everything out of the bowl without clogging.

We also learned that dual flush toilets cleanse the bowl with what is known as a washdown flush.  Washdowns can create a little unpleasant splash action.  You know what I’m talking about.

H2Option adds more push to the water from under the rim of the bowl. We engineered the water pathways so that when the water is released from the tank,  some of it is diverted to the rim where there are a series of chambers. The air in the chambers pushes the ongoing coming water forcefully out into the bowl, pressurized, but not mechanized, so it’s a quiet action.

There is no sound associated with the added force; and a lot less splashing.  The marketing types call it “Staying Clean While Going Green,” which actually is one of their better headlines.  This is the kind of thing we get to invent at the American Standard New Product Design Center.