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Do Low-Flow Toilets Really Work?

Of course they do

The federal government decided that after 1994 toilets shouldn’t use any more than 1.6 gallons of water per flush. Manufacturers had to comply, but by most accounts their early efforts were a flop.

That was a decade and a half ago. The redesigned low-flow models that followed work as well or better than older models that used as much as 7 gallons of water per flush. There is, in fact, a joint U.S.-Canadian evaluation program called Maximum Performance (or MaP) that uses soybean paste encased in latex to see just how well these low-flow toilets work. And most of them work very well. Test results are easily accessible on the Internet.

High-efficiency toilets use even less water than standard low-flow models, some as little as 1.1 gallons. Dual-flush toilets, which have separate flush modes for solid and liquid waste, are another water-saving option. The differences in performance may seem trivial, but switching from a standard to a low-flow toilet can save thousands of gallons of water per year.

Replacing an old toilet with a low-flow model is a simple and fairly inexpensive way of conserving resources—a cornerstone of green building.

More Info:

To learn more, see the Residential Toilets
section of our Product Guide


  1. | | #1

    Low flow...the bio diesel of toilets
    The Roman idea of moving waste with water from one place to another is bad to begin with. Expensive infrastructure and costly "treatment" plants are industrial society dead ends. Design for the planet, not for ridiculous ideas.


  2. | | #2

    Low flow... the bio diesel of toilets
    Fill us in, MS. Are you talking about a change to composting toilets or do you have something more? No flame. Inquiring minds...

  3. | | #3

    Low flow - an idea whose time has come
    I have 3 bathrooms, 2 of which had low-flow toilets which go back several years. I kept one old high-volume toilet for "serious" use. Sometimes the low-flows had to be double-flushed, which seems to defeat the purpose. These are not cheap toilets. Recently I remodeled the third bathroom and installed a new low-flow toilet and it works the best of the 3. Not one double-flush required in 6 months of use. It appears that the technology has caught up with the promise.

  4. | | #4

    Low flow toilets
    Low flow toilets are a great idea, but some manufacturers haven't designed them well. I have a Ko**er that I have to use the plunger on several times a month. I called them about it and they blamed the "deposit", not the toilet!

  5. | | #5

    Low flow...
    "Recently I remodeled the third bathroom and installed a new low-flow toilet and it works the best of the 3."
    Which toilet actually worked? I've seen many bad reports, it would be nice to have a good one.

  6. GBA Editor
    Martin Holladay | | #6

    Low-flow toilets
    I'm happy with my Toto Drake CST744S (C744 bowl, ST743 tank). It scored well on the MAPP test (a test involving the flushing of turd-shaped pieces of miso) -- it flushed 900 grams of miso in the test.

    I paid $211 a couple of years ago.

  7. | | #7

    Cheap Effective Low Flow Toilets
    So far, the best LowFlow I've found is the Niagara Flapperless (unfortunately, only available at Home Depot.) It's only $98 and it scored 1000 on the MaP tests- that means it reliably removes 1000 grams (2.2 lbs!) of "solids" w/ one flush, at 1.28 GPF. It doesn't have a flapper, so one less part to fail and the valve is made by FluidMaster, so it uses a standard seal.

    The down side is that all the parts except the seal are unique, and HD, in their wisdom, doesn't stock repair parts, although Niagara says they're working on that.. Niagara is also willing to quick ship repair parts, but that could take several days. Also, the supplied seat is too cheap and the supplied wax ring is a throw-away- spend the $$ for a good one.

    I've installed half a dozen at my Fellowship as part of our Green Sanctuary program. So far, the user feedback has been good and I haven't had any maintenance problems. It's only been a few months, but at this point, I'm recommending them to my friends..

  8. | | #8

    Gerber Low flow thought me how to use a plunger
    I bought two Gerber low flow toilets in 2003 and have since worn out several plungers. We learned to slush half way through the job. They are the WORST toilets I've ever seen!! I find myself staying late at work so I can use their toilet...

    I paid extra money for them because I liked the look. Last month I went to our local project center and bought a replacement for one of them in hopes I could find a crapper that works. WOW, what a difference! I come home early from work again.

  9. | | #9

    Low Flow toilets are a joke.
    A toilet is a sanitary device meant to minimize contact between people and their turds after they leave the body. Yet, thanks to the low flow toilet I've had to use the plunger more in the last 10+ years than in my previous 40-years on this planet.

    Because of the propensity of these things to plug up, I normally have to flush 2 - 4 times to get the turds and paper down the pipe. How is that saving water?

    I used to work for NREL (National Renewable Energy Lab), a bastion of hippie engineering and all things green. I have created a NREL (Nuclear Rectal Evacuation Load) scale borrowed form the Fujita tornado rating system. A F1 NREL is rare and requires 1 flush to get the solids and paper into the system. A F5 NREL is the most serious situation. Any time the toilet plugs up, it is automatically assigned a F5 rating even if one round of the plunger is needed to unplug the crapper. This is done for the annoyance factor of having to use the plunger.

    Thank you to the U.S. Gummint for meddling in people's private business...again.

  10. | | #10

    Low Flow toilets are great!
    We replaced our old toilet with a Toto about three years ago. It flushes very well, and has saved us a lot of water, especially since we were subject to water rationing last year.
    We have to double flush sometimes, but really only about as often as we had to with the old clunker.

  11. | | #11

    Niagra flapperless
    I installed one of these ( I am a DIY type) over two years ago. They do a great job. Sometimes two flushes are required but very seldom. No parts issues in over two years of steady use. Do get a good quality seat.

  12. | | #12

    Try Caroma
    Those who have had bad experiences in the past, should try a dual flush. Caroma is the best, but there are other good models out there as well. The Caroma has a totally different trap design than a traditional low-flow toilet. AND... you get what you pay for with these kinds of things!! Don't expect to pay less than $100 for something and it work as well as something that costs more. The reason it costs more is because they have an army of engineers working on it for year and years. Why would you complain about something not working when it's obviously just some company trying to jump on the green bandwagon without doing the proper work to adapt their technologies.

  13. | | #13

    Low Flow toilets + use rainwater
    Here in australia dual flush is the norm - 3litre +4.5litre full flush being the new standard - I have one and it works fine ( Caroma).

    To save even more water attach a rainwater tank to your toilet and flush with rain water - we get a rebate on the tank installation if we connect laundry and/or toilet to a rainwater tank.

    I do all our laundry with rainwater too using a front loader washing machine - our mains (town) water usage is now sub 50 litres a day per person ( state government target is 155 litres per day per person ).

  14. | | #14

    Kohler Cimarron works very well
    My wife got a Kohler Cimarron under the tree last year (it had a big red bow on it). Not only was she delighted, the kids were thrilled! I installed it in an oversize closet upstairs. It works much, much better than the original high-flow avocado-colored toilet downstairs.

    On the NREL scale, an F1 every single time.

  15. | | #15

    Low Flow- very good with some challenges
    I installed a couple of Caromas at the cottage and they are wonderful since all sewage is hauled out by truck. They will pay for themselves in a couple of years. In towns & cities, the challenge that I have heard from infrastructure people is that the sewage systems were not designed for low flow and the amount of plugged mains has gone up. Perhaps MS is right, we should all use composting toilets.

  16. | | #16

    "Ultra Flush" Systems
    Our pressurized units have never required more than one flush... no plunger at all, ever.

  17. | | #17

    Low Flow
    I put in Kohler about 18 years ago, always using a plunger on them and double flushing. In the process of changing them over to American standard they seem to work flawlessly

  18. GBA Editor
    Martin Holladay | | #18

    15 posts by "Anyonymous"
    If your toilets are so good, why not provide your name so we know who is recommending these wonderful toilets?
    Thanks for all the good suggestions.

  19. | | #19

    Low Flow Toilets
    I installed three Kohler low flow toilets several years ago and they worked great. The problem is the sewer line from the house to the sewer manhole was 210 feet away. The money I saved on water cost me $1,800 to have a Sewer Jet Cleaning Company flush the sewer lateral. Low flow toilets are great water savers but flush three times to save on the unexpected consequenses of modern technology.


  20. | | #20

    which toilets work
    I have 6 apt buildings. Kohler toilets do not typically work; take several flushes. The American Standard toilets work with one flush.

  21. bobbomax | | #21

    A Nonny Mouse
    I just figured out how to set up an account- that's why I showed up as anonymous. (GBA, please note, it's not obvious how to register for a free account.)

    I recommended the Niagara Flapperless. I'm not associated w/ Niagara, but, aside from the caveats I mentioned, I'm impressed w/ the Niagara functionality and price, so I would like to see it do well in the marketplace.

    People like to say, "You get what you pay for.", but in fact, you can pay a lot and still not get much value. The Big Orange Box near me has a whole rack of toilets, ranging from 50 to 300% more expensive than the Niagara, with MaP scores ranging from 30% to equal to the Niagara, with no correlation between price and performance rating. Or perhaps, there's an inverse correlation- the cheapest toilet gets the highest posssible rating, and I believe it has the best design, although I won't really KNOW that for five years.

  22. GBA Editor
    Martin Holladay | | #22

    Thanks for the feedback
    Thanks for the feedback on our registering process. We'll look into whether it can be improved.

    You make an important point about the lack of correlation between toilet price and toilet performance -- which is exactly why the MaP performance tests are so valuable and important.

    Thanks for your contributions.

  23. | | #23

    My Low Flow Works Great
    We just did 2 bathroom with Toto's EcoDrake 1.23 GPF and they work Great. I occasionally have to flush twice but I also had to do that with a non low flow toilet. and They're about the same price as a standard toilet would have been. It seems to use some sort of suction that kind of jets everything out of the bowl. Best flush on the market (and no, I'm not affiliated) i think, my office has their 1.6 GPF and it also works very well.

  24. | | #24

    my american standard

  25. | | #25

    Low flow toilets
    While the latest generation of low flow toilets may work, (I'm not fully convinced), the pipes they are hooked to may not clear with only a gallon and a half of water. So the new toilet is more of a band-aid on a scab.

  26. | | #26

    Low Flush
    I installed 2 Mansfield Eco-flush toilets in my house 5 years ago. I soon found out the I had problems with the drain line. Once that was repaired, they work great. I also installed the new hi tech sprinkler nozzles on my sprinkler system and an ET based sprinkler clock. The water supplier now pays me Ha Ha

  27. | | #27

    Low flow doesn't always work
    In California we have to replace all toilets with low flow. I did with a 1.6 Eljer High Seating low flow toilets. The only problem is that if you have a turd in there over 10" long it doesn't go down. Even with three or four flushes. Plunger time.
    In Europe they had low flow toilets but they always flushed every time. I know I gave some of my best work and they still handled the load, so to speak. Of course their tanks are up on the wall about 6 ft up, with a literal chain that one pulls. Some times the old ways are better than the new ones.

  28. | | #28

    Dual-Flush to Avoid
    Heads Up: Though the styles looks great, the guts of the Renovators Supply dual-flush toilets are flimsy, and the destructions are in Chinese. They also had promised a client of mine delivery again and again, until she finally cancelled her order. The buttons on top never seem to align with the internal mechanism, which is brittle plastic, not of a style you can easily get replacement parts for at the local store. Thanks for all your reviews!

  29. metamerman | | #29

    Hard to find good information, but we like Eco Drake II
    Picking toilets took me longer than any other single decision when building our new house. There's so much bad and conflicting information out there, and so many variations even within one model of one brand, each with different performance. We ended up buying several different toilets and trying them and then putting the ones we didn't like in our rentals! Our final choice was Toto Eco Drake II 1.28 ADA sanagloss. Spend the extra bucks to get the cyclonic versions. We've never had a clog, very rarely have to double flush (unlike *all* of the dual-flush toilets we tried), and because it has a relatively large water surface area and good washdown, you don't have to use a brush any more often than with the old 3.5-5 gallon toilets. Toto does make some other good models, but we wanted some of ours to be right hand flush which is not available in any of the one-piece models.

  30. user-1068185 | | #30

    Composting toilets
    Since I want to build a new, green house, I have toyed with the idea of using a composting toilet. But it seems you have to have a basement or crawlspace foundation for them to be installed properly. Does anyone have any experience with these kind of toilets? Could you install them with a slab-on-grade foundation?

  31. GBA Editor
    Martin Holladay | | #31

    Response to Barbara A. Smith
    Several manufacturers make composting toilets that can be installed on a slab; one that I am familiar with is manufactured by Sun-Mar. Here is a link: Sun-Mar self-contained units.

    For more information on composting toilets, see:

    Composting Toilet Systems

    Hoping for experiences with grey-water and composting toilets

    You can also Google "composting toilets" to learn more.

  32. quarc | | #32

    7 gallons?!
    WTF do you do with 7 gallons per flush. I have seen your toilets and they suck!
    Here, in Europe, the standard tank is around 7,5liters(about 2 US gallons.) with the option to empty half the tank.
    I seldom have to flush twice.

  33. GBA Editor
    Martin Holladay | | #33

    Response to Andrew P
    Since 1994, federal regulations in the U.S. have required toilets to use no more than 1.6 gallon per flush. Before then, most toilets used up to 3.4 gallons per flush, although a few models (especially older models) may have used up to 5 gallons per flush.

    I remember the publication of Stop the Five-Gallon Flush in 1973; that book was a landmark volume calling for more efficient toilet designs. Even then, I remember that critics accused the authors of exaggerating, since most toilets used less than 5 gallons per flush.

    If any toilets ever used 7 gallons per flush, they were uncommon.

  34. joecolo | | #34

    Low flow toilets waste water
    I can only speak to my own experience of the low flow toilets at my place of business. When I enter the stall I often flush the toilet to remove the existing residue. When finished I more often than not flush twice to get a proper operation.

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