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Dual Flush Toilets

Updated on October 26, 2011

Dual Flush Toilets

What to look for in a toilet

Things to look for when buying a new toilet (not necessarily in order of importance):

1. Low water consumption (if you flush your toilet 20 times per day, a savings of 20-100 gallons/ day is possible if you replace your toilet, depending on how old it is. As much as 35,000 gallons per year.

2. Durability, low maintenance

3. Flush performance & flushing mechanism: Recently there has been great advancement in the design of the trap and flushing mechanisms to achieve superior flush performance with far less water. Powerful flushes can be noisy..but they do help keep the bowl clean.  Pressure-assist toilets require at least 25 psi of water pressure to function correctly. If in doubt, you can check your home's water pressure with an inexpensive gauge (available in hardware stores). If your home has low water pressure, go for a gravity toilet, which can work well with levels as low as 10 psi.  Some of these mechanisms can be more expensive to repair or replace. 

4. Surface area of water: I have noticed that more surface area means waste does not land directly on the porcelain

5. Ease of Cleaning: Does the bowl stay relatively clean with use? (S.A. of water and power of the flush can help keep the bowl clean) Are their a lot of nooks and crannies that gather dust and dirt?

6. Comfort: How does the flushing handle feel? (you will probably grasp this handle thousands of times each consider it a major quality of life issue. Flimsy handles are depressing. Is the seat comfortable? Is it the right height? (ADA models that are higher are available) Is an electric seat warmer a vain and frivolous luxury or a necessity? Oval seat or round seat? Oval seats are considered more comfortable if you have the space.  Acoustical comfort: Soft close seat to avoid the loud echoing noise of a carelessly dropped lid.

7. Aesthetics and style: color choices, compatibility with bathroom style, seat material

8. Ease of installation

9. Dimensions There is some variability in toilet size...and shape, be sure you select a toilet that fits with adequate clearances on all sides. One key dimension that varies is the distance of the waste-line from the back wall.

10. Availability of replacement parts

11. Price including available rebates

12. Embodied energy of the toilet: how much energy does it take to ship a toilet from Australia or Japan? How much energy goes into the fabrication of the toilet? Is it made from recycled materials?

13. Recyclability: will the manufacturer take the toilet back and recycle the parts when it is made obsolete by future advancements in the technology?

Researching Toilets

I recently invested in two new toilets for my residence in Berkeley, California. Like most people, I had never bought a new toilet before. So I did some research. I searched on the internet for sites comparing different models and offering performance test results. I visited local suppliers, such as Home Depot and inquired about the models on the floor. For example it is possible to purchase a shiny new toilet for less than $200, seat and wax ring included. When I inquired as to why this model was so cheap, I was told that the trap was not glazed...and therefore is easily clogged with waste that cannot smoothly slide through to the plumbing line. On a side note, I discovered that Urban Ore, a building materials salvage yard in Berkeley, California sells used toilets and toilet seats. The used toilet seats are way overpriced. In fact, they typically cost more than brand new ones. Used toilets are a better deal...but In my opinion it makes no sense to spend the time and energy refurbishing and installing obsolete technology, no matter how charming. Perhaps some creative person will discover a great use for obsolete toilets and they will have a second life.

Back to the topic. EBMUD has good information on the performance of different models and also available rebates for purchasing what they call a "High Efficiency Toilet" Performance ratings depend on water usage and also the success of the flush. A toilet that uses little water but needs to be flushed several times to eliminate the waste is clearly worthless. The EPA has a good resource for all types of watersense fixtures.

I was motivated in my selection by a concern for water conservation, and I admit that there is some question in my mind about the trade off of the disposal of my perfectly good but waterhog old toilet and the water savings. I have not done the extensive research that would be required to determine the precise effect of my toilet replacement on our happy survival as a species, but since I am an architect I figured it was worth a bit of consumption to educate myself.

Below you will find a comparison of the two toilets that I chose. In summary, they are both fine, except for the problem of not enough water in the bowl to keep waste from smearing the porcelain. The solution to that problem might very well be a device called flushmate. This is a pressure assisted flushing system. According to the manufacturer it forces waste at 70 gallons/ minute, strong enough to clean the bowl with every flush. The pre-flush water level in the bowl is also higher, which helps keep the bowl clean as well. Many different toilet manufacturers offer the flushmate system at 1.6 gal/ flush, 1.0 gal/flush, or less. The flushmate website has links to them. Make sure you claim your rebate money if you install one of these high efficiency toilets!

Toto Aquia

Caroma Caravelle

Toto Aquia and Caroma Caravelle Comparison

The two toilets that I selected were the Caroma Caravelle and the Toto Aquia

Both have a dual flush mechanism, allowing the user two options for water usage depending on what they are flushing and how much water might be required. (1.6 and .8 gallons for the caroma and 1.6 and .9 gallons for the Toto. Compare this to older models that typically use between 3 and 7 gallons per flush) Both have what I would descibe as modern lines...mainly an aesthetic based on functionality, not traditional toilet aesthetics and nostalgia. Both have sleek bases that are easy to keep clean...not a lot of nooks and crannies for dust and bathroom scum to collect.

Other assessments:

1. It seems like even less water is needed for flushing only urine. (the caroma does better in this area)

2. I recently tiled my bathroom floor ( a couple of years after the caroma was installed.) Unfortunately I did not carfully study the unusual way that the caroma is meant to be installed with screws into the subfloor at the rear. I drilled holes through the tile and subfloor and now there is nothing for the screws to bite into. So my toilet is not solidly attached to anything and therefor rattles around a bit.  Real bummer.  I prefer tha standard american attachment method.  

3. Both of these toilets have one BIG problem.

Because of the low water level in the bowl, and a low surface area of water, they need to be cleaned with a brush every time someone defecates. I am all for saving water, but I am not sure how this problem can be solved. Perhaps there needs to be a pre-dump lever to add more water to the bowl when user anticipates taking a dump. Maybe you can learn to aim.

Time to look into waterless composting toilets?

Gerber Dual Flush

I have first hand experience with the Toto Aquia and the Caroma. Definitely mixed reviews...I like the way they look and they are sleek on the outside...easy to keep clean...but the bowl staining is a problem. My brother chose a Gerber toilet (highly recommended by Terry Love) that has a power assist flush and a large surface area of water. I don't think it is very good looking, but if aesthetics are not a primary concern for you, this might be a good choice.

This toilet also comes in a wide array of colors...which might appeal to the more daring among you.


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    • profile image

      Dominique B. 5 years ago

      About 4 years ago, I first bought a Toto Aquia for our powder room when we lived in Canada. We did not like it because we needed to clean it after each use! I even had the Toto sales representative come by our house to measure the level of water. I could not believe that it was correct. He joked and told me Toto also invented the toilet brush and they are making money on that too. So for an upstairs bathroom, we bought a Neptune Parma FB1625. As chic as the Toto, it's design is beautiful. But even if it was a dual flush toilet, the shape of the bowl kept the water where needed and kept it clean like a regular toilet. I highly recommend it. We , since then, heve moved to LA and I am in the process of changing my toilets for dual flush. I will do anything to find here the Parma from Neptune.

    • profile image

      nomopo 6 years ago

      I installed a Toto model CST744 five years ago and am very pleased with it. I just wanted a dual flush model with easy to clean sides for my other bath, but seeing the poor reviews maybe I should just buy another CST744.

    • profile image

      FreeGalgt 6 years ago

      In my home the previous/current owner (my GF) installed Caroma. I have tried to reposition my butt and my aim for the past 18 months. I am very, sick and tired of 'cleaning' the remains of my 'business' or flushing multiple times - the use of chemicals to clean the toilet after EACH use does not seem Eco-friendly... Give me a real flushing toilet~!

    • profile image

      sjohnson 6 years ago

      thank you for the details you gave. i enjoyed reading it. and hopefully to read more from it.

    • sarahd profile image

      sarahd 6 years ago

      Jc1 -

      There are many water-saving toilets that perform very well. go to this website:

      to find a toilet that can flush almost anything in one 1.6 gallon or less flush.

    • profile image

      jc1 6 years ago

      For everyone that is complaining about the water level in the toilet bowls and having to clean the toilets more frequently this is because of Al Gore and the environmental controls that were placed on toilets. I wish I had kept my old toilets because they filled the bowl sufficiently and you could flush once and it would be clean so now you may have to flush twice just to rinse the bowl so HOW IS THAT SAVING ENERGY EFFICIENCY. HELLO WHO TESTED THESE TOILETS AND WHO REALLY LOOKED AT HOW EFFICIENT THEY ARE???? So much for QA and LOGIC. And as the one person mentioned, yes you have to do a lot of research because there are so many requirements in ref. to buying a toilet. I did a lot of research and searched hi and low to find an old fashion toilet because I knew the new toilets conserved water, there are none to be found. The trap on the toilet limits the water as well so are they really energy efficient no way.

    • profile image

      JRICE 7 years ago


    • sarahd profile image

      sarahd 7 years ago

      peanuts - that sounds very environmentally sound and all, but what do your neighbors think? Maybe you should buy a composting toilet.

    • profile image

      Nannie Jean 7 years ago

      I have two bathroom suites from the 1970's in my house. One is maroon and the other is light pink. They were all the rage back then, its more slate and caramel colours now.

    • profile image

      peanuts 7 years ago

      i took my toilet out last year and have still not replaced it ... i am getting sick of pooping in my backyard.. maybe i'll try one of those toto's

    • profile image

      Christian Paulsen 7 years ago

      Inax, Japan's other toilet manufacturer, makes a series of dual-flush HET's that clean the bowl with every flush. These toilets swirl the water in the bowl. In addition, 100% of the water comes from the top. These toilets are a much better alternative to the Toto and the Caroma models. See the Inax website at

    • profile image

      Phil 7 years ago

      Caroma used to be popular in New Zealand, imported from Australia but have rapidly lost favor over the past few years. Over here they have staining of the porcelain issues, out of shape issues and are made cheap and WAY overpriced. Even locally the support is crap and plumbers stay well clear, I would advise you to too, buy a Toto or ANYTHING else!

    • profile image

      DavidD 7 years ago

      The caroma toilets may be an engineering marvel but it is foolish to invest 500.00 in a toilet that has to be cleaned daily and leaks. We have had the Caroma Caravelle for just over a year - total cost was just over 1400.00 (500.00 for toilet, 500.00 for install. 150.00 for diagnosis plus taxes)

      The toilet leaks at the seal, the seat loosens weekly and the stains from deficating make the toilet an embarassment and a nuisance.

      As soon as we have enough money saved up the caroma is getting introduced to a sledge hammer and I am going back to a 6l full bowl system. It would have taken me a lifetime to waste 1400.00 in water - being water conscious hsa cost us 1400.00 and an estimated 150.00 is toilet bowl cleaner.

    • profile image

      David  7 years ago

      The Mansfield dual flush design is not as easy to repair as your simpler ball and chain with flapper designs. For example.. if the floater tube starts sticking to the seal at the bottom, you have to take the whole tank apart to replace the red seal at the bottom... Simpler is always better...!!

    • profile image

      steven R 7 years ago

      Caroma three years old and going strong. Unfortunately I tiled the bathroom floor and had to reinstall the toilet. This model of caroma has a non-standard method of attachment to the floor and the method poses some problems. Instead of bolts on either side of the flange, it screws into the subfloor at the back. When I drilled through the tile I mistakenly drilled through the subfloor as nothing for my screws to attach to. ANYWAY, it looks like they fixed this problem on newer models and now have more standard closet flange bolts. MAKE SURE the model you buy has this improvement!!! Also check this out:

    • profile image

      klkcda 8 years ago

      What a coincidence! The two you list above: the Caravelle one-piece and Toto Aquia are exactly the two I'm debating between after researching, reading reviews and speaking with friends who have the Toto (and love it I might add). But still a difficult decision for me. I love the sleek look of the Toto though from the side it looks like a huge cruise ship; I love the look of the Caravelle too-a little less imposing and I love the comfort height. It may win out because it seems as good as the Toto but I prefer the comfort height and anyone with a tall stature might also appreciate the difference. But the Toto Aquia III has a long delivery time and I need my unit within the next couple of weeks rather than wait all summer. Concerns: it's the numerous comments about having to clean after each payload that slightly concerns me as far as having guest over and their embarrassment. Why can't the manufacturers ensure a Sanagloss finish right through the unit to make payload easier to slide? Hmmm...Corningware has a cleaning product for their casserole dishes that leaves it silky smooth. I used it on top my fridge once for a wonderful slippy finish that seemed to repell dust. Wonder if rubbing a new toilet interior down with that would ease payload through the trap any better. No wait, I forgot a salesperson told me to be careful not to void my warranty. For instance I was told NOT TO use those blue 'pucks' or it would void the warranty. So I guess I won't chance putting anything other than what's is recommended in the toilet I choose. I never would have thought choosing a toilet would be such a big decision.

    • profile image

      Group B 8 years ago

      Terry Love indicates on his website that the Gerber DualFlush toilets are garbage, as they use the WDI EcoFlush system.

      Apparently there are a bunch of problems with this system.

    • profile image

      martin 9 years ago

      why not try tri flush toilets?

    • profile image

      Chris Chambers 9 years ago

      The cost of water and sewer prices continue to increase in the US. Dual flush toilets are a great buy.We rpovide some very unique dual flush toilets on our website

    • profile image

      Jason 9 years ago

      I just purchased and installed this Toto Aquia dual flush. Yes, the water level in the bowl seems low. I don't have a problem with anything sticking to the side of the bowl. If you position your butt so that the fecal matter drops down into the water, then there's no problem. If you have the squirts and/or can't control where your fecal matter drops, then almost any toilet will need extra scrubbing. The only issue I have with the toilet was the installation being "different" than other toilets I've installed. In all, I think it is a strong flushing, efficient and stylish toilet.

    • profile image

      dan 9 years ago

      I installed the Toto Aquia in my onsuite. It looks great but I should have did more research. Toto, you really dropped the ball on this one. Didn't any of your researchers take one home and have a dump? This is ridiculous, you should supply a life time of toilet brushes or send a clean up crew every day to my house. If anyone is going to buy one of these dual flush toilets in a country where water is not an issue, then do not buy a dual flusher until they somehow raise the bowl water level. These dual flushers are great ideas but they have not reached the point where they are practical yet..............Sorry Toto

    • sarahd profile image

      sarahd 9 years ago

      njarif- you should buy a toilet with a power assist flush- it cleans the bowl as it flushes!


    • profile image

      njarif 9 years ago

      I made the mistake and replaced my 15 yr old toilet with a single piece 1.6 G St Thomas brand, which cost me $360.00. The new toilet looks great but, it must be brushed after each use and multiple flushes do not clean the surface. Are there toilettes that swiril the water? Wish I had kept the old toilet.

    • profile image

      autism4me 9 years ago

      I just want a super flush toilet with a big hole that my special needs child will not stop up every time she poops!!!!

    • profile image

      toto toilet 9 years ago

      whoa, i never realized how many different things there are to look for in choosing a toilet. thanks for the helpful post.


    • profile image

      Wendy 10 years ago

      We just installed the Toto dual flush and haven't had any problems with remnants sticking to the bowl. (I see that the above comments are from a few months ago - do we have a newer model?) It does, however, seem to get and stay dirty very quickly. I was thinking of getting the Caroma for our other bathroom, but it sounds like that has the same problem. Anyone know if the 1--piece Caroma is better in this regard?

    • profile image

      Shawn 10 years ago

      I use a Gerber Ultra and it is such sweet satisfaction I often hate to get up! Just don't powerflush your little gem while sitting unless you intend to shower...

    • profile image

      Brian 10 years ago

      "2. Both of these toilets have one BIG problem." Bingo. Every day I deal with this. I don't see how I'm saving any water when I must flush multiple times to get "it" all off or clean the brush when I have to resort to deeper cleansing. I've tried to raise the water level on my Caroma, but it doesn't seem to raise the level in the bowl, only the reservoir.

    • profile image

      Kent Miller 10 years ago

      As a North Carolina small business we feel it's our duty to make a contribution towards water conservation, and providing high quality Dual Flush Toilets (DFT's) at factory direct pricing is our way of doing such.

    • sarahd profile image

      sarahd 10 years ago

      Barbara, I am not sure what you mean by using fresh flush to clean your flush...but maybe you are onto something. Perhaps toilets should have a self cleaning super-power flush option. Or the washlet seat could turn in on the bowl itself and go to town. Toilet brushes are so unsanitary.

    • profile image

      barbara gilman 10 years ago

      I purchased a kohler flush. i am inquiring whether I ca use Fresh Flush to occassionally clean my flush. Which I very seldon have to do

    • darron profile image

      darron 10 years ago from New York City

      I like Toto Washlet, but can't afford it yet. My butt is one of the butts with the smiley face on it for the ad campaign, but still can't afford one:(

    • profile image

      Kurt Bramstedt 10 years ago

      Well, I have to admit being partial to Caroma as I am the Regional Manager for Caroma.

      Early in the article you mention the trap not being "porcelinated" which I assume means glazed. Whetther the trap is glazed or not does not impact the performance of the toilet. If the glazing is not done correctly, snags can be created which catch toilet paper and affect the performance of the toilet.

      You must also look at the size of the trap or passageway through the toilet. Most toilets in the USA are of the siphonic design in which a siphon is created to pull the waste down. In order to create the siphon, their trap must be small and they will glaze it to maximize their performance. But the small trap tends to create clogs.

      Caroma uses a washdown design in which all the water comes from under the rim and washes down the bowl. Caroma also uses a 3.5 to 4" trap which will not clog, and in some cases can pass a baseball. The trap in a Caroma toilet is usually unglazed.

      I would suggest you ask for the Sydney 305 from Caroma. It is their new low cost model. It will flush 700 grams of solid waste on the half flush and 1000 grams on the full flush. Note that Caroma is the only toilet manufacturer to test their toilet performance on the half flush.

    • profile image

      Mark 11 years ago

      We installed the Toto a year ago and like them very much.

    • barranca profile image

      barranca 11 years ago

      Just used one of these recently. Very satisfying.

    • Ralph Deeds profile image

      Ralph Deeds 11 years ago from Birmingham, Michigan

      Sounds like a Royal Flush!

    • profile image

      s matthews 12 years ago

      Very interesting, I guess it is the Toto for me. thank you sarah

    • pauldeeds profile image

      Paul Deeds 12 years ago from Berkeley

      I prefer the toto--it's much easier to keep clean, and seems less flismy. The only down side is the flushing mechanism, a button in the tank isn't near as satisifying as an old-school flushing lever. In addition, with the half flush button imbedded in the same small circle as the full flush it's rather easy to give it careless full flush, especially when you have big fat fingers like me.


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