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Dual-Flush Toilets 'Wasting More Water Than They Save' (theguardian.com) 136

An anonymous reader quotes a report from The Guardian: Toilets specially designed to save water are wasting more than they conserve, the UK's largest water firm has warned. Campaigners have warned for years that dual-flush toilets, introduced as more efficient alternatives that were expected to use less than half the amount of water per flush, are more prone to leaks. The problem is said to be so great that the costs are outweighing the benefits.

"Because there's so many loos that continuously flow all through the day and night, collectively that water loss is now exceeding the amount of water the dual-flush design should be saving," said Andrew Tucker, water efficiency manager at Thames Water. "The volume of water loss is getting bigger every day as more people refurbish and retrofit older toilets and as more homes are built, so it's a growing problem." Thames Water said poor design and materials cause water to flow continuously into the bowl. And, according to the BBC, the Bathroom Manufacturers Association has acknowledged that the design of many dual-flush toilets is inherently more prone to leakage.
"The majority of them use the drop valve system, which sits at the bottom of the cistern and opens to allow the water to flow out when the flush is pressed," reports The Guardian. "Debris and other issues can cause the mechanism to fail to close, meaning water continually flows from the cistern and into the bowl."

"Older cisterns tend to use a siphon system, which works by pushing water upwards until it reaches a point at which it can flow into the bowl. Because that point is above the waterline when the toilet is not being flushed, the system is less likely to develop the same sort of leak." Jason Parker, the managing director of Thomas Dudley Ltd, one of the UK's largest plumbing manufacturers, told the BBC: "If we're serious about wasting water and we want to stop it, the only way to do that is put a siphon back in."
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Dual-Flush Toilets 'Wasting More Water Than They Save'

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  • Comment removed (Score:4, Insightful)

    by account_deleted ( 4530225 ) on Wednesday September 30, 2020 @08:06AM (#60556898)
    Comment removed based on user account deletion
    • Also, they're not very good at pushing down a large turd the first time. I suppose it's more environmental to somehow chop it up in pieces (use your imagination) before using a gentile eco-friendly flush?

      That is a setting issue. The flow for the #2 is set too low - or you eat a lot of roughage and you shit a lot of floaters.

      • I've never heard of a dual flush system...

        So, you have to literally flush these things twice to get what is normally done in one flush on regular toilets?

        If so, I fail to see how this would save water in the first place?

        • No. It means you have two buttons. One for a smaller flush, one for a larger flush.

        • So, you have to literally flush these things twice to get what is normally done in one flush on regular toilets?

          No, it means you have two controls:

          * One is a smaller flush for getting rid of pee.

          * The other is a full-on flush for the mastodon-worthy logs your mother drops.

        • I have taken to multiple flushes as I poop, to prevent a jam. I do the same thing for wipes, 4 wipes, flush, 4 wipes, flush.

          Also, there's a slow toilet leak probably worth 2-3 flushes a day.

          Also toilet use is inconsequential in Calirornia, where the vast majority of water is grandfathered into watering a desert so we can have vegetables all year long. Thank you for suffering limit discs for this, Californiaites.

          Anything else on this 30 year long innumeracy plague? Nope. Can't think of it.

          • by tragedy ( 27079 )

            The problem here is mostly poorly designed toilets and plumbing. If the flush isn't powerful enough, then that's generally not that not enough water is used, it's that there's not enough pressure. There are flushing systems that can produce a lot more pressure even when only using a small amount of water, but I don't think I've ever seen one in a home in the US.

            • Gravity-Fed Toilets (Score:5, Informative)

              by BigBlockMopar ( 191202 ) on Wednesday September 30, 2020 @12:28PM (#60557802) Homepage

              it's that there's not enough pressure. There are flushing systems that can produce a lot more pressure even when only using a small amount of water, but I don't think I've ever seen one in a home in the US.

              Our toilets are much the same here in Canada - residential use toilets are gravity-fed with typically 6L per flush from a "close-coupled" tank which is mounted directly on top of the bowl. The tank is filled from municipal or well supply, which is typically at 50PSI or so, but the fill valve is the only part of the system under pressure.

              They operate by momentum, not by pressure. m1*v1 = m2*v2. The pressure would be limited by the head, which is typically only 2 feet or so. The secret to their effectiveness is allowing 6 kilograms of water to accelerate as quickly as possible in the height allowed by the design and have it collide with the ...dark matter... to drive it away.

              Most residential plumbing systems use 1/2" ID supply pipe which would simply not allow a pressurized flush like a commercial toilet to be effective. There are exceptions which use bladder systems to attempt to leverage the standing water pressure of the municipal water supply to drive the flush water down to the bowl as quickly as possible. These systems tend to be expensive, unreliable, and loud, although one day these issues may be resolved.

              Improvements to the existing system will require very carefully designed bowls and trapways and exceptionally well-installed plumbing with regard to soil pipe slope and venting. My own home is outfitted with 3L per flush toilets which do an admirable job [watermatrix.com] - I have yet to clog them, even after a visit to a buffet restaurant - despite being purely momentum-based close-coupled toilets without the additional complexity and failure-prone seals in dual-flush mechanisms.

              Adding technology is not the answer to this problem. Keeping it as simple as possible but doing the basics really well is key.

              • by Strider- ( 39683 )

                The actual issue is the increased back pressure against the outflow due to either old cast iron pipe, and/or too long of a horizontal run before the vertical drop.

              • The flow you get from the tank to the bowl is minimal...it's really just getting the siphon effect started. This is where all the flushing power comes from.

              • by tragedy ( 27079 )

                For generating pressure, I suppose it's elegant, or whatever, for everything to work just through water pressure, but it's not like homes without electricity are actually a thing. There's no particularly good reason that an air pump and pneumatic pressure couldn't be used. Or how about negative pressure in the actual drain, or any number of other systems. Or, they could simply do it the way old fashioned toilets did it and put the toilet tank up near the ceiling. If people have some problem with the way tha

          • "Also, there's a slow toilet leak probably worth 2-3 flushes a day."

            It doesn't flush anything though, it just keeps it wet and clingy in the tubes.

        • There is also a dual flush with a greedy cup (Pythagoras cup) siphon that does half flushes if you pull and hold the handle. If you pull the handle and drop it it gives a full flush. It's how European toilets work.

          In the US, we tend to use a flapper at the bottom drain. It still leaks, but when it does, it's less of a dribble and more of a every 15 minutes your toilet is filling itself again thing. The flapper leak is easy to hear and fix. The greedy cup siphon will be completely silent as it wastes
        • It's normal flush versus low flush. If you're only peeing then you don't need a big flush so you use the low flush button. At work we have these, though it's a pull-up versus push-down lever.

    • Re:Turd pusher (Score:4, Insightful)

      by Applehu Akbar ( 2968043 ) on Wednesday September 30, 2020 @08:20AM (#60556924)

      Also, they're not very good at pushing down a large turd the first time...

      This article is not talking about the US low-flow toilet that wastes water because you always have to flush twice. The European design has 'big flush' and 'small flush' buttons. The real problem is, why after all these centuries can't we design a flushing mechanism that doesn't leak?

      • We can. People continue to expect the cheapest and are unhappy with the result.

        Both my toilets are dual flush. They do not leak.

        They also have never (and never anywhere have I had it) limescale build up despite being in a hard water area. some people just create their own problems through lazyness and stingyness (I am both but no to the point of false economy though!).

        Trouble is the gorvernment madate things like you will fit this for x reason and then leave the specs requirement up to the manufacturers and

      • Maximum efficiency is the 'big flush' and 'no flush' system; "If it's yellow, let it mellow. If it's brown, flush it down." I grew up in the country with a well that often ran dry in the summer. You learn to conserve quickly when it's a necessity.
        • by necro81 ( 917438 )

          a well that often ran dry in the summer. You learn to conserve quickly when it's a necessity.

          I'm hoping that the upcoming release of Dune will result in an increased awareness for water conservation. Maybe not to the point of everyone wearing stillsuits, but some heightened consciousness would be a boon to humanity.

          • I'm hoping that the upcoming release of Dune will result in an increased awareness for water conservation. Maybe not to the point of everyone wearing stillsuits, but some heightened consciousness would be a boon to humanity.

            What an enchantingly uninformed yet fantasy-based life you must live.

          • But doesn't that strongly depend on location?

            I mean - if my location has enough rain and the rivers and lakes never run dry (though drinking water is taken from deep underground), then all I'm wasting by keeping the tap running 24/7 is my money and the energy that was used to pump the water.
            The water goes from underground, through various pipes, then to my sink, then to the sewers, then waste treatment and finally to the river. It's not like the water disappears or anything,

            • You would be wasting capacity in the water processing facilities. Probably increasing the use of chemicals in pre and post consumption processing. Depending on the aquifer in question, you might be contributing to eventual depletion. In some cases human use is outpacing refilling and that will come to an end eventually.
      • Re:Turd pusher (Score:4, Insightful)

        by jbengt ( 874751 ) on Wednesday September 30, 2020 @08:39AM (#60556984)
        Parent is exactly right.
        From TFS:

        "The majority of them use the drop valve system, which sits at the bottom of the cistern and opens to allow the water to flow out when the flush is pressed," reports The Guardian. "Debris and other issues can cause the mechanism to fail to close, meaning water continually flows from the cistern and into the bowl."

        From TFA:

        Thames Water said poor design and materials cause water to flow continuously into the bowl.

        So it is not about dual-flush, it's about a leaky design, a type of flush mechanism that most non-dual-flush water closets also have (at least in the USA and the EU, apparently not in the UK).

        • So it is not about dual-flush, it's about a leaky design, a type of flush mechanism that most non-dual-flush water closets also have (at least in the USA and the EU, apparently not in the UK).

          It's almost as if you come to slashdot for the accuracy of the headlines, not the fascinating detective-work needed to figure out what they really meant to say.

        • So it is not about dual-flush, it's about a leaky design, a type of flush mechanism that most non-dual-flush water closets also have (at least in the USA and the EU, apparently not in the UK).

          What he's saying is that people are 'upgrading' to dual-flush to be eco-conscious but the quality of those units suck so they're doing more harm than good.

          Does the dual-flush concept mandate a non-siphon mechanism? That may be another possibility. Certainly low-quality doesn't help but the endeavour itself may be qui

          • Pressure on water resources in the south east of England (aka Thames Water patch) is among the highest in the world. Then again about 20% of the water entering their pipes never makes it to a tap.

        • by spitzak ( 4019 )

          Yes, it sounds like the "bad" system is the form used by EVERY toilet in the USA. The valve is at the bottom of the tank and at no point does the flushing water go higher. This siphon design seems to be some European or UK thing and not suprisingly higher quality than the garbage we get in the USA.

          Also I am suprised how many ignorant people there are here who think this is some kind of low-water toilet or that you have to flush twice. I have a dual-flush toilet in my home in the USA. It is generally availab

      • And most US toilets also use the bottom-of-the-tank flush method, so they're all prone to the same sort of leaks. I've never found it hard to notice the water running and fix the leak.

      • by skids ( 119237 )

        We have dual flush knobs at work on commercial-style toilets, in the U.S. They'd be great, if they were all installed in the same direction rather than having to look around the knob for the sticker with the little arrows, and weren't obviously made of sub-par materials.

      • Toilets get better. My parents got a low flow back in the 80s and they hate it and they advise everyone to never get one. But they get clogs more from the pipes and becuase that design they got is not good. I have used other low flow toilets that work just fine without troubles. But once someone has a bad experience with a new device they will continue to hate anything like it for decades.

        • by spitzak ( 4019 )

          This is not a low-flow toilet. It has two types of flushes, one of which is more conventional. I guess the small one is equivalent of the low-flow toilet. The idea is you use that when the low-flow will work and save a lot of water.

    • by jbengt ( 874751 )

      Also, they're not very good at pushing down a large turd the first time

      That has nothing to do with dual-flush. Dual-flush is the regular amount of water for turds and a lesser amount for piss.
      Also, I have an older water closet, which uses considerably more water than the mandated new low flows, and still still doesn't always flush completely flush away turds.

    • However I think people Urinate more per day, than defecate a day.
      75% of all flushes are to get rid of Urine, (and some toilet paper for women) in which that process takes little water.

      In public restrooms Men have Urinals which are more efficient than toilets. However at least in America, Urinals are not common in residential bathrooms.
      If you want real water savings you will need a lot more expensive setup. One for Urinating and one for Defecating.

      The Good Old 'Merican Toilets use a lot of water bu

    • by AmiMoJo ( 196126 )

      It's because they are badly designed. The basic design hasn't changed since Victorian times, except to move the tank lower down and reduce the pressure.

      Compare with these Japanese models: https://youtu.be/P2QnlYA4Ngs [youtu.be]

      The water starts relatively high to prevent splashback. The water accelerates and swirls around the bowl, cleaning it. Some models have a small tank for detergent that is mixed in. Then there must be a valve or something because it gets flushed away hard, and finally refilled.

      The amount of water

      • by denzacar ( 181829 ) on Wednesday September 30, 2020 @10:01AM (#60557284) Journal

        Every toilet is a swirl-flush toilet when you position the flush pipe at an angle to the bowl and not center-aligned with the toilet bowl.
        It's just that most plumbers are not really... what's the word... bright.

        Just look at Mario brothers and their fascination with mushrooms and alternative medicine and lifestyles - instead of with plumbing.
        FFS That one time Mario pretended he was a licensed physician and he went around just randomly throwing pills at people.
        Seriously... When will FDA or DEA do something about that crime family? Lives are at stake!

        • by PPH ( 736903 )

          Every toilet is a swirl-flush toilet when you position the flush pipe at an angle to the bowl and not center-aligned with the toilet bowl.
          It's just that most plumbers are not really... what's the word... bright.

          The geometry is a function of how the bowl porcelain is cast. I doubt a plumber can do much about it once the (cheap) toilet is delivered to the job site.

          • Unless the user insists on a square toilet bowl, all toilets are spherical.
            And a plumber just needs to angle the fuckin pipe so it flushes along the rim and not straight down into the hole.

            It can be done simply by NOT aligning the tank and the pipe with the center of the bowl, setting it instead slightly (like, centimeters) to the side when mounting the tank.
            Unless one has one of those "concealed" or combined-with-toilet-bowl tanks...

            Then again some people hammer nails into their own testicles for fun.

        • by AmiMoJo ( 196126 )

          It's more than just the angle of the pipe, the shape of the bowl accommodates it and ensures that with the available velocity it cleans the entire thing.

          I don't think I've ever actually seen Mario do any plumbing. Must be a cover for something. The regularity with which Peach gets kidnapped makes me think maybe he's trying to get away from him.

          • Most bowls are spherical. Flush liquid along the sides of a spherical bowl and it will go around and down.

            As for the Mario family... Not to be promoting stereotypes... But they ARE Italian.
            You know... Like Corleones, Sopranos...

    • I suppose it's more environmental to somehow chop it up in pieces (use your imagination)

      Well, you have to wash your hands anyways.

    • by Kisai ( 213879 )

      I've only run into maybe two of these between all my relatives, and trust me, they're not very good.

      Instead of working the first time, you have to flush 3-4 times the #2 button, and it's like, no, this is not superior at all unless your #2 is closer to liquid in the first place, and even then, you may still find yourself flushing twice.

      The ideal, proper, toilet would be designed to use both the hot and cold water, and use that to make sure the water, and toilet is at room temperature, and have a "self-clean

    • The double flush ones I have used are much better at this than normal toilets. This type of toilet is the small versus large flush style, and the large flush is indeed bigger than normal in my view.

      This is a British article. The reason for the leaks tends to be the more American style of toilets with a valve at the bottom of the tank rather than the more traditional (for UK) siphon systems. My own normal toilet is indeed more prone to slow leaks with that style if I don't keep that gasket clean. I'm sayi

    • Do something else with the turds, eh?

      Trump has you covered. Didn't you hear his five-word cognitive test result at the debate?

      "Screaming, angry, Trump, fling, turds".

      Right in the faces of any somehow-still-undecided voters.

  • I guess he has never have a flapper valve shit the bed.
  • by aaarrrgggh ( 9205 ) on Wednesday September 30, 2020 @08:24AM (#60556934)
    Hands-down the foam wash, vacuum/composting toilet systems use the least water and are the lowest environmental impact and minimize sewage treatment. But they have higher up-front cost and do require ongoing maintenance.
  • typically the UK loses 170 billion litres of water a year in the water network before it reaches the household...

    maybe just maybe they should fix the leaks in the network they control

    https://www.ofwat.gov.uk/

    • Comment removed based on user account deletion
    • It is a "thing" in the US too. My city alone flushed 6B gallons in 2018. https://www.kxan.com/investiga... [kxan.com] So if the UK is only losing 170B L (44B gallons) that probably is not too bad. Austin is a mid sized city and is losing 6B. I also had a long argument with the city about the new waller creek project, which is both flood control and a continuous flow destination park with pumps to keep the flow going all year round. Problem is that flow causes extra evaporation when it is being pumped instead of natura
    • It simply can't be governmental.
      Cause neo-libs don't believe in things like societies or... you know... sanity.

      They also just LOVE the sound of trickling liquids.
      It's a urination fetish which arises from castration anxiety. A highly common issue among conservative humans.

  • Dual flush siphons are easy to find. 2 part designs remove the need to remove the cistern to replace/repair them, which was the other argument for switching to the new versions.

    Still facing an uphill struggle getting my wife to remember how to use the short flush though, without separate buttons to do it. Will still save me hours next time I need to repair the damn thing and not have to worry about checking for leaking pipes either.

  • by magarity ( 164372 ) on Wednesday September 30, 2020 @08:41AM (#60556994)

    From what I get out of the summary this is a problem of design with the mechanism being used, not the concept of dual flush. Make sure to understand where the real problem is and attempt to solve, don't just blame the concept because of poor implementation.

    • by magarity ( 164372 ) on Wednesday September 30, 2020 @08:46AM (#60557018)

      "Debris and other issues can cause the mechanism to fail to close, meaning water continually flows from the cistern and into the bowl."

      It sounds like a bigger issue here is why is debris in the water system??

      • by Roger_Wilco ( 138600 ) on Wednesday September 30, 2020 @09:16AM (#60557124) Homepage
        I live in a region with heavy water. Everything gets a little calcium buildup on it over time, if you don't have a water softener. Also, the rubber seals wear out and leak over time. In North America, pretty well all the toilets I've seen are the drop valve system. When a drop valve toilet fails, it leaks. If it leaks a little, it leaks a little continuously. A little leak is bad. When a siphon toilet fails, it's harder to get it to flush. If it leaks a little, it's a little harder to get it to flush (you might need push a little faster to get it to work). A little leak is irrelevant.
        • I live in a region with heavy water. Everything gets a little calcium buildup on it over time, if you don't have a water softener. Also, the rubber seals wear out and leak over time. In North America, pretty well all the toilets I've seen are the drop valve system. When a drop valve toilet fails, it leaks. If it leaks a little, it leaks a little continuously. A little leak is bad. When a siphon toilet fails, it's harder to get it to flush. If it leaks a little, it's a little harder to get it to flush (you might need push a little faster to get it to work). A little leak is irrelevant.

          Yeah, but you can hear it leak ... so if you hear it, you fix it.

      • by AmiMoJo ( 196126 )

        A lot of it will be due to hard water. The UK has a lot of that and it eventually breaks and blocks everything.

    • I'd argue that the problem to solve is the one where people can't be bothered to fix a leaking toilet.

      • I'd argue that the problem to solve is the one where people can't be bothered to fix a leaking toilet.

        In all fairness this is hard to detect unless you hang out in the bathroom listening closely to the toilet. Doesn't really occur to people to do that.

        • You don't have to hang around after flushing. It's instantaneously obvious the moment you enter the toilet.

        • I'd argue that the problem to solve is the one where people can't be bothered to fix a leaking toilet.

          In all fairness this is hard to detect unless you hang out in the bathroom listening closely to the toilet. Doesn't really occur to people to do that.

          A leak of less than litre(s) an hour is not observable without help, try a drop of blue food dye in the bowl. If your dye fades away you have a leak. Putting dye in the tank may help narrow it down to a bad float or valve if you cut off the water supply. Old style american pot, ymmv.

    • by idji ( 984038 )
      Why didn't they use a dual siphon instead of valves? Was it so that it was really light to press?
      • When they work properly they work better than a siphon, dumping water fast enough to instantly start siphoning round the u-bend and suck everything away before swirling starts. When they work properly...

  • Here in England, the dual flushers have one big button and one small button. They are never labelled but I assume it's small button for small flush. Or is it big button for the more frequent small flush? Is it supposed to be intuitive? Also I find the small button a bid awkward to press so often end up pushing both. I prefer the twin lever system - hold for long flush.
  • The original high flow toilets used as much as 11 liters, but got down to about 6 liters before the dual flush and low flow were introduced.

    Dual flush are toilets with 2 buttons, one for 6 liters, another for 3 liters.

    Low flow toilets have just one button and use 4.8 liters.

  • Someone should design a toilet that has a "garbage disposal" type mechanism to shred everything that gets flushed. This could also help avoid any clogs be it from too much paper or a large amount of feces.
  • In my experience they typically require more flushes to end up with a clean bowl. I've never really understood the need in the first place when the UK has so much rain water that the water companies regard it inefficient to fix many leaky mains supplies.

    https://www.bbc.co.uk/news/bus... [bbc.co.uk]

    • by ledow ( 319597 )

      The real solution is to deliberately use grey-water to flush toilets. It doesn't need to be perfectly filtered, chlorinated, flouridated water to just force a turd round the U-bend into the sewer where it's instantly classed as foul water.

      Every British roof has a gutter. Top up the cistern with that and allow overspill into the sewer, it's no different. And if it's a dry spell then the refill can pull in clean water if that's what you want to do.

      Like the bathroom-sink-that-drains-into-the-cistern... geni

  • I have owned and repaired many toilets in America over the years and every one of them had the sort of rising plug at the bottom of the water tank that is blamed for leaks and problematic flushing here. None of these toilets had any problems with leaking unless the rubber plug was completely worn out. I think some other problem is the cause the British leakage described here.

  • Correlation does not imply causation, idiots. The difference is in the type of mechanism, not in whether there are one or two buttons to flush.

    I sort of had the unfounded idea that news for nerds would imply that news by idiots would be filtered out, but I was wrong.

    (Nevertheless, I found this actually quite interesting news, especially since I was not aware of the ingenious way those ancient toilets I have not seen for at least 30 years worked.)

  • by superdave80 ( 1226592 ) on Wednesday September 30, 2020 @11:45AM (#60557634)
    The other problem with 'low flow' is that you need a minimum amount of water to push the sewage through the sewers themselves. San Francisco had to start adding chemicals into the water to help break up the sewage that was no longer flowing. https://www.sfgate.com/bayarea... [sfgate.com]
  • Flush twice (Score:3, Insightful)

    by stikves ( 127823 ) on Wednesday September 30, 2020 @11:56AM (#60557690) Homepage

    I learned to instinctively flush twice for number two. The first one does not work most of the time, and I don't want to leave anything behind by mistake.

    Except for very high velocity commercial ones, the regular flushes are no longer sufficient for their primary purpose. Also the sewage systems are not designed to work with that little amount of water. That causes blockages down the pipeline, and cost even more to unclog.

    Why do we, as human societies, optimize a single parameter at a time, without looking at the larger picture? Don't we have any actual engineers to look at tradeoffs in the designs?

  • we have 2 dual-flush toilets. 1 is 8 years old, and the other is 2. So far, so good.
    If UK's toilets are leaking, then they need a redesign on the flush mechanism.
  • So it's got nothing to do with dual flush... Most toilets I see these days have this drop valve system, In reality, all toilets I've seen in the houses I've been living have a system like that, and I'm 46 now.. The difference with dual flush (in most cases) is just how long the opening is open.

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