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Dual Flush Toilet Buyer's Guide: Eco-Friendly High Efficiency Toilets for a Green Home

Updated on October 11, 2018
Chris Telden profile image

Chris Telden has a B.A. in sociology, was a supervisor in a large library for many years and worked many more years in administrative roles.

Dual flush toilets, designed to be green and leave a low impact on the environment, are already popular throughout Europe, Asia and Australia - and even mandatory in some locations. For the consumer, a dual flush toilet is an efficient way to save money while conserving fresh water resources.When flushed, older, standard 3.5 gallon toilets use more than double the water of dual flush toilets, which use just 1.6 gallon per flush at maximum. Installing a dual flush toilet or doing a conversion or retrofit means serious savings to the water bill and a worthy effort to be eco-friendly and environmentally conscious.

This buyer's guide to dual flush high efficiency toilets covers everything you need to know to convert to using these water efficient commodes in your home.

Toilet Statistics

According to the Environmental Protection Agency (EPA), toilets used in the home use 2.1 trillion gallons of water every year, which comprises 30 percent of all water used in the home.

What is a Dual Flush Toilet?

A dual flush toilet is a high efficiency toilet (HET) that conserves water by offering a choice of two different flush volumes - a low volume flush for liquids and a full volume flush for solids.

Replacing an old standard toilet with a new dual flush commode, or doing a dual flush toilet retrofit on your existing fixture, can help phase out the use of water guzzling toilets.

Efficiency Standards for High-Efficiency Toilets

The National Energy Policy Act of 1994 required toilets sold in the U.S. to use no more than 1.6 gallons per flush. High efficiency toilets have stricter standards. The maximum effective flush volume for a high efficiency toilet is 1.28 gpf (gallons per flush) on average.

If you have a single flush toilet, for it to be considered high efficiency by WaterSense standards, it has to use no more than 1.28 gallons of water per flush. If you have a dual flush toilet, the full flush option must use no more than 1.6 gallons per flush and the low flush option must use no more than 1.1 gallons per flush - according to the EPA, this averages out to the 1.28 gpf requirement.

Where to Buy

Locally, dual flush toilets may be purchased at hardware stores and home supply stores.

Online, sells a wide selection of one-piece and two-piece models, including one of the most popular models, the Caroma 989646W Caravelle One-Piece Dual-Flush Toilet.

Alternatively, you can buy a conversion kit (also called a retrofit kit) to convert your existing toilet into a dual flush setup.

See below for additional models of dual flush toilet and retrofit kits offered.

Comparison of Dual Flush Toilets Models and Specs

To find model numbers that qualify for high efficiency toilet rebates, check out:

If you want to buy a dual flush toilet, but aren't yet sure which model to get, find detailed information on selected toilet models.

Or view a longer list of dual flush toilets in 1-piece, 2-piece, economy, and elite models.

How Much Water is Saved

Per flush, a dual flush toilet works out to saving from a third of a gallon to almost four gallons of water per flush, depending on the current efficiency of your toilet.

Who Invented the Dual Flush Toilet?

The first dual flush toilet was designed by the Australian, Bruce Thompson in 1980. In the dry climate of Australia, Thompson was working to design a more water-efficient toilet for Caroma. It was called the Duoset cistern. This basic design was used in new construction over most of Australia until 1994, when the toilet went through another redesign to further improve water usage efficiency.

What Is a High Efficiency Toilet With a WaterSense Label?

A WaterSense label on a toilet means that the toilet has been certified in third party laboratory tests to be not just high efficiency, but high performance as well, in many cases flushing with more powerful pressure than standard toilets. According to the Austin Water Utility Conservation Division, a WaterSense label toilet must successfully flush 350 grams of waste.

The WaterSense program is sponsored by the Environmental Protection Agency. Replacing your single flush toilet with a toilet with a WaterSense label means saving up to 4,000 gallons of water every year.

Aside from any tax breaks, rebates by local utilities, and other governmental incentives to switch to a high efficiency toilet, a family of four can save about $90 per year and about $2,000 over the toilet's lifetime on the water bill.

The EPA advises that if all Americans replaced their residential toilets with WaterSense labeled toilets, total water consumption would be reduced by almost 640 billion gallons of water.

How Does a Dual Flush Toilet Work?

Unlike standard toilets, which siphon large quantities of water through a tube to eliminate waste, dual flush toilets utilize the power of gravity and a larger diameter trapway design to whisk waste matter away with far less water. Since waste has a wider area to go through, this also means less clogging.

Buying Tips

Bathroom Dimensions and Dual Flush Toilet Size:

Make sure the toilet you choose fits in the bathroom space available. Measure your bathroom and the space available for the toilet model you select. Note down available floor space and wall space.

Also measure the distance from the floor bolts to the wall behind the toilet. It should be 10", 12", or, less commonly, 14" and ideally should match the "rough in" distance of the toilet. Or, get a toilet with an adjustable rough-in to accommodate both 10" and 12" distances.

1 Piece or 2 Piece:

  • Choose one piece toilets if you're leery of cleaning - they're easier to clean than two pieces.
  • Choose a two-piece toilet if you want to save money and aren't afraid of frequent toilet cleaning.

Toilet Bowl Shape:

  • Choose an elongated toilet bowl for optimal comfort in a spacious bathroom.
  • Choose a round toilet bowl if the bathroom space available is cramped.

General Tips:

  • If you have low water pressure, make sure the dual flush toilet is a gravity toilet - and most dual flush toilets are - rather than a pressure-assisted model, which needs a 25 psi water pressure.
  • If you're trying to qualify for a rebate, make sure the model number matches the one with the WaterSense label in the EPA list of WaterSense toilets.

See Reviews of Selected Dual Flush Toilet Models Now


Because of their innovative design, dual flush toilets reduce both water usage and the number of occasions when the toilet gets stopped up. But like any fixture, dual flush toilets aren't perfect. The main problems are:

  1. Dual flush toilets can be more expensive than standard American toilets.
  2. Less water standing in the bowl can mean more residue and possible odor. Dual flush toilets require regular cleaning.

The EPA has a page on myths about problems with high efficiency toilets.

HET High Efficiency Toilet Rebate Programs (use scroll bar at bottom to see full table)

(click column header to sort results)
High Efficiency Toilet Rebate Program URL  
Arizona, Cochise
Arizona, Flagstaff
Arizona, Peoria
Arizona, Tempe
California, Fresno
California, Mountain View
California, Otay
California, Riverside
California, San Diego
California, Sonoma County
Canada, Alberta, Calgary
Canada, Ontario, Toronto
Canada, Ottawa
Colorado, Boulder
Colorado, Denver
Colorado, Westminster
Florida, Miami-Dade
Georgia, Austell{060B147D-5AE5-4DA2-9B4A-8578F621697E}
Georgia, Cobb County
Georgia, Gwinnett County
Georgia, Marietta
Massachusetts, Concord
Massachusetts, Walpole
Montana, Bozeman
North Carolina, Durham
North Carolina, Raleigh;/pt03/DIG_Web_Content/category/Resident/Water_and_Wastewater/Cat-1C-2009513-144902-WaterSense_Toilet_Replac.html
Oregon, Portland
Texas, Austin
Texas, San Marcos
Washington, Bellevue
Washington, Olympia
Washington, Pullman
Table of High Efficiency Toilet Rebate Programs in Different U.S. States and Canada

Review Summaries of Selected Models

Here is information about selected models of 1 piece and 2 piece dual flush commodes, from Caroma, American Standard, Toto and Kohler. These descriptions come with specifications and review summaries to help you decide on the best dual flush toilet for your needs and budget. About these summaries: I read numerous detailed reviews and then reported on what I read. Note that new reviews are always being added to models; I try to update this page as I see new reviews but don't always keep up as well as I should, so check out the latest ones for yourself.

1 Piece Dual Flush Toilet: Caroma 989646W Caravelle

Manufacturer: Caroma
Model Number: 989646W
Dimensions: 29 3/4" L x 14 3/4" W x 28 1/2" H - bowl is 14 3/4" high
Rough-in: 10" - 12"
Bowl Shape: Round
# Pieces: 1 piece
Features: Concealed trapway, seat is included, ADA compliant
High Efficiency Toilet & WaterSense Label: Yes
Accessories not included: Toilet seat, Caroma Caravelle Round Toilet Seat White 301032W

Summary of Reviews at

  • Pros: Very popular. Used all over Australia, works the best of other models tried, low flush mode sometimes successfully flushes solids, too, water efficient, no problems, last for years, bowl stays clean, easy to maintain, good looks, good height, compact, easy for a novice to install, works better than standard toilets.
  • Cons: A few reviewers noted a "sewer smell." This may be due to the repeated complaint that they observed a low level of water in the bowl, which leaves residue behind.

2 Piece Toto Aquia II Dual Flush Toilet

2 Piece Dual Flush Toilet: Toto Aquia II

Manufacturer: Toto
Model Number: CST414M
Dimensions: 27 1/4" D, 30 1/4" H, 14 1/8" W
Rough-in: 12"
Bowl Shape: Elongated
# Pieces: 2 piece
Features: Comes in various colors, Quiet
High Efficiency Toilet & WaterSense Label: Yes
Accessories not included: Elongated toilet seat, needs a Washlet adaptor (product # THU9090)

Summary of Reviews at

  • Pros: Good looks, saves water, easy to install, easy to clean, operates well, good price, reviewer who is a "green interior designer" uses it and recommends it, preferred over Kohler by one reviewer
  • Cons: One reviewer found low flush pressure and an uncomfortable seat.

Summary of Reviews at Homeclick (Update June 1, 2013: Unfortunately, Homeclick doesn't seem to have this in stock anymore and the reviews are no longer displayed):

  • Pros: Stylish looks, water efficient, economical, lasts, "fun," low flow half flush works so great full flush is usually not even needed, soft close lid, surfaces are easy to clean, good technical assistance from the manufacturer
  • Cons: Somewhat hard to install, needs frequent cleaning, flush button labels could be clearer for guests, sound of water running while using (before flush), those with ceramic tile floors might want to hire a plumber to install to avoid drilling, seat doesn't stay in "up" position for one reviewer.

Economical 2 Piece Dual Flush Toilet: American Standard 2566.216.020 FloWise Right Height Elongated Seat, Complete

Manufacturer: American Standard
Model Number: 2566.216.020
Dimensions: 29.75" x 29.63" x 19.5", bowl rim is 16.5" high
Rough-in: 12"
Bowl Shape: Elongated
# Pieces: 2 piece
Features: Concealed trapway, seat is included, ADA compliant
High Efficiency Toilet & WaterSense Label: Yes

Summary of Reviews at Home Depot (update 6/1/2013 - I had to remove this source link, as Home Depot is no longer displaying this product or the reviews. These reviews were really there when this article was published, even though I cannot link to them now.) :

  • Pros: Good looks, easy to install (even easier with two people), easy to clean because of skirting, very water efficient, full flush clears the bowl well, short fill time, water level normal for dual flush toilets, ADA height seat.
  • Cons: Problems flushing toilet tissue down with the low water setting. Dual flush button could use labels for guests. Required longer water supply line to install and new wax ring for one reviewer. Very little water standing in bowl, leaving organic residue. Toilet is too high.

Kohler K-3564-0 Saile Elongated Seat 1 Piece Dual Flush Toilet

1 Piece Dual Flush Toilet: Kohler K-3564-0

Manufacturer: Kohler
Model Number: K-3564-0
Dimensions: Compact, 28-1/2" L x 14-1/4" W x 28-3/4" H
Rough-in: 12"
Bowl Shape: Elongated
# Pieces: 1 piece
Features: Easy to clean skirted trapway, Quiet-Close toilet seat
High Efficiency Toilet & WaterSense Label: Yes
Accessories Not Included: K-7637 (Angle Supply With Stop) and K-9384 (Dual Flush Actuator)

  • Pros: (based on one review at eFaucets): Installation "easier than...expected," good looks, low water usage, easy to clean, compact.
  • Cons: (based on 8 reviews on Several reviewers found problems, including difficulty of installation, a sticky flush button, difficulty of access to the water supply after installation, small exit diameter.

Economy Dual Flush Toilet: Caroma Caravelle 270

Manufacturer: Caroma
Model Number: 270
Dimensions: 14 1/4"W x 29"L x 32 7/8"H. Bowl is 15" high
Rough-in: 10" - 12" adjustable
Bowl Shape: Elongated
# Pieces: 2 pieces
Features: European styling, 2 button flush mechanism, large trapway
High Efficiency Toilet With WaterSense Label: Yes
Accessories: Must get seat separately

Summary of reviews at

  • Pros: Saves water, lasts for years, easy install, low maintenance
  • Cons: May take a little longer to install, needs more cleaning

Kohler Escale Dual Flush Toilet K-3588-0 2 Piece

2 Piece High Style Dual Flush Toilet: Kohler Escale K-3588-0

Manufacturer: Kohler
Model Number: K-3588-0
Dimensions: 26-15/16′′ x 15-3/8′′ x 32-3/4′′
Rough-in: 12"
Bowl Shape:  Elongated
# Pieces: 2 piece
Features:  Comes in white or almond, European Style, comes with seat, top mount flush actuator, mounting hardware included, backup shut-off valve in tank
High Efficiency Toilet & WaterSense Label: Yes
Note:  This model doesn't use a regular floor flange - it bolts to the floor.  You're advised to read the installation instructions before you buy it and have a professional plumber do the install.

Summary of Reviews at eFaucets:

  • Pros:  Aesthetics, water savings, would recommend the toilet
  • Cons: Hard to install

Dual Flush Toilet Retrofit

If you're on a budget, looking for an economy model of dual flush toilet, a general rule of thumb is to choose a dual flush gravity toilet with a round seat in a standard white color.

Another option, which is far less expensive than getting a new toilet, is a dual flush toilet retrofit or converter kit. Rather than replace the siphon toilet, you get a kit that allows you to save water with two flush options.

Read the author's disclosure statement about compensation for this article.


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