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Science

Should You Flush With Toilet Lid Up Or Down? Study Says It Doesn't Matter (arstechnica.com) 132

doc1623 shares a report from Ars Technica: Scientists at the University of Arizona decided to investigate whether closing the toilet lid before flushing reduces cross-contamination of bathroom surfaces by airborne bacterial and viral particles via "toilet plumes." The bad news is that putting a lid on it doesn't result in any substantial reduction in contamination, according to their recent paper published in the American Journal of Infection Control. The good news: Adding a disinfectant to the toilet bowl before flushing and using disinfectant dispensers in the tank significantly reduce cross-contamination. [...]

The scientists conducted their experiment with E. coli (as a host bacteria) and coliphage MS2; the latter is not a human or animal pathogen but serves as a useful model. The public toilet used in the experiment was located in a stall in the restroom of an office building. That toilet was tankless, relying on water-line pressure for flushing, with no lid and a U-shaped seat with a gap in the front. The home toilet was a standard siphonic toilet with a tank and lid in a private residence; there was no gap on the center of the seat. Toilet bowls were seeded with MS2 and flushed. After one minute, samples were taken from various restroom surfaces: the top and bottom of toilet seats, the bowl rim, three locations on the floor, and the right and left walls. The team also conducted a similar experiment involving cleaning the bowls with toilet brushes, both with and without Lysol toilet bowl cleaner. All those samples were then tested for MS2 contamination.

The results: both the tops and bottoms of the lidless public toilet seats had more contamination compared to household seats, but otherwise, there was no statistical significance in the degree of contamination between lidless public toilets and household toilets with lids. And the surface contamination did indeed persist even after repeated flushes. The toilet seat was the worst offender with the greatest degree of contamination, which the authors suggest "reflects the airflow that occurs during toilet flushing, i.e., largely around the top and bottom of the toilet seat." That same airflow is likely a factor in spreading the contamination to restroom floors and walls. Perhaps the least surprising finding is that rigorous cleaning with a toilet bowl brush and Lysol reduced the contamination by 99.99 percent compared to cleaning with just a brush. Therefore, "The most effective strategy for reducing restroom cross-contamination associated with toilet flushing include the addition of a disinfectant to the toilet bowl before flushing and the use of disinfectant/detergent dispensers in the toilet tank," the authors concluded. They also recommend regularly disinfecting all restroom surfaces after flushing or cleaning with a toilet brush in health care facilities -- which often have a lot of immunocompromised people -- and if someone in your house has an active infection like norovirus.
The findings have been published in the journal American Journal of Infection Control.

Slashdot reader doc1623 writes: "This headline brought me joy today, so I thought I would share (I could honestly care less about reading the article but joy is joy, I take it where I can find it.)"
This discussion has been archived. No new comments can be posted.

Should You Flush With Toilet Lid Up Or Down? Study Says It Doesn't Matter

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  • by Joe_Dragon ( 2206452 ) on Thursday February 01, 2024 @11:39PM (#64207522)

    Arizona has that kind of water to waste?

    • by jhoegl ( 638955 )
      In comparison to the surrounding states, Arizona consumes the least amount of water in relation to Colorado river.

      The problem is more the aquifer and its unregulated use.
      • Re: (Score:3, Insightful)

        And California is demanding a bigger share of the Colorado river because they don't know how to manage their water supply worth a shit. LA has a naturally very large aquifer that they don't even use, because instead of maintaining storm basins to replenish (like Arizona does, literally by the thousands in Phoenix alone) they channel 90% of it directly into the ocean. Last time I mentioned this some progressive derp was all "hurrdurr you can't drink water out of the dirt!" because apparently they've never he

        • The city will sink into the ocean if LA pulls water from the aquifer.
        • California has over 5x the population of Arizona so yes, I would expect California to use more water. Is there something surprising about that? LA's storm basin's were never designed to capture drinking water so it's currently a massive engineering project. https://www.nbclosangeles.com/... [nbclosangeles.com]

        • by HiThere ( 15173 )

          California needs more water because it's naturally a desert, and it's got a huge population. It's also a prime area for agriculture.

          Move the population to other states, and the requirement for water would drastically shrink.

          Basically, all over the country people are extracting more water than the yearly rainfall. You normally hear of this as "The water table is getting lower" or "You need to dig your well deeper". In places with more people, and less rain/snow, this becomes obvious more quickly. But it'

          • California needs more water because it's naturally a desert, and it's got a huge population. It's also a prime area for agriculture.

            No it's not, only a small portion of it is. Nor does desert mean "needs more water", actually the opposite is true because desert native flora use much less of it. If you need more water in a desert, you're doing it wrong. California does a lot wrong though, which is news to nobody.

            Move the population to other states, and the requirement for water would drastically shrink.

            Meanwhile, California's population has actually decreased while its neighbors have increased, yet California thinks it has a right to more water, simply because it's California.

            Basically, all over the country people are extracting more water than the yearly rainfall. You normally hear of this as "The water table is getting lower" or "You need to dig your well deeper". In places with more people, and less rain/snow, this becomes obvious more quickly. But it's not very localized. IIUC the problem even exists in Florida and Louisiana.

            That's nice, though Phoenix, which is entirely deser

    • by ghoul ( 157158 )
      Toilet water is just pre-irrigation water.Think of the alfalfa. Do your bit to support the alfalfa export industry. Flush 2-3 times.
    • To flush toilets? Yeah. To grow rice? No. I bought a smart toilet which has a UV light in the basin. It is supposed to eliminate odor. The toilet is in a very small room about 3x7 ft within the restroom, so someone can shower or use the sinks / countertops while another person is in the toilet room. My main floor restroom is the only one with the toilet in the same room as the sink, but all of them are "smart". You don't push flush. You leave the toilet and it intelligently knows to close the lid, and flush
  • by mlheur ( 212082 ) on Thursday February 01, 2024 @11:48PM (#64207532)

    Keeps countertop stuff from falling in.

    Treats everyone the same: lift, use, close.

    Aerosolization of the toiletâ(TM)s contend, but I guess the article contradicts me here.

    2 out of 3, still worth closing the lid.

    • Counterpoint:

      The lid creates underpressure and thus reducing suction when flushing, so the number of times you get stray-floaters after flushing goes up
      (those are mostly only discovered by the next person who lifts the lid because the flusher never checked).
    • Keeps countertop stuff from falling in.

      some people have tiny cramped toilets so i might concede this one

      Treats everyone the same: lift, use, close.

      how is that a reason lol

      Aerosolization of the toiletâ(TM)s content

      if you spend your time worrying about microscopic particles of shit, you have OCD. 100%. Its Howard Hughes type shit

      • by tlhIngan ( 30335 )

        Treats everyone the same: lift, use, close.

        how is that a reason lol

        Obviously you're male and single, and likely never had a date that mattered.

        Because the female population generally get very persnickety if you should leave the toilet seat *up*, especially at night, and take great offence if you would even dare suggest that they can put the seat down before going.

        Arguments about toilet set up or down have raged on since it was invented, and it's often the men who are obligated to lift the seat up, do their

    • Keeps countertop stuff from falling in.

      Treats everyone the same: lift, use, close.

      Aerosolization of the toiletâ(TM)s contend, but I guess the article contradicts me here.

      2 out of 3, still worth closing the lid.

      (4) It's not a decorative water feature
      (5) It keep the dog from drinking out of it

    • Agreed - just good social etiquette. An easy rule for the neuro diverse slashdot crowd to remember too.

      The kids sometimes make a stink and don't use the brush - I'm sure the lid reduces the amount of pong released (even though there are some gaps around it). I guess that depends on how many draughts you have though.

      I wonder about their methodology though - waiting just 1 minute after the flush doesn't seem very long. If there's a real "plume" then it could spread around the whole room, but take many minutes

      • Agreed - just good social etiquette. An easy rule for the neuro diverse slashdot crowd to remember too.

        The kids sometimes make a stink and don't use the brush - I'm sure the lid reduces the amount of pong released (even though there are some gaps around it). I guess that depends on how many draughts you have though.

        I wonder about their methodology though - waiting just 1 minute after the flush doesn't seem very long. If there's a real "plume" then it could spread around the whole room, but take many minutes to actually land on surfaces. I'm sure they thought of this and have a reason for doing it the way they do, but it's not the same as how a real toilet gets used.

        Next up, an investigation of farts - which are obviously shit adjacent. I know, I know! Trump was on to something when he suggested UV lights up the old Hershey Highway. UV lights to sanitize farts! A new age of cleanliness awaits.

    • 4. Keeps the cat / dog from using it as a water bowl.
  • It's because the humidity is zero in AZ and the bacteria dry up
    • That's mostly just Phoenix, which is in a valley, which is why it gets a lot of heat. UofA is in Tucson. Two hours north of Phoenix is Flagstaff where there's a LOT more humidity (and snow.)

      • That's mostly just Phoenix, which is in a valley, which is why it gets a lot of heat. UofA is in Tucson. Two hours north of Phoenix is Flagstaff where there's a LOT more humidity (and snow.)

        Yes. Flagstaff's weather is a lot like Pennsylvania weather.

  • I hold my breath and close my eyes whenever someone is using one near me.
    • Seriously, fucking germ blasters. They never get cleaned and the seams are caked in biohazard filth, guaranteed. So fucking gross
      • by gweihir ( 88907 )

        You do realize that people usually wash their hands before using them, right?

        • by Zocalo ( 252965 )
          Let's say they use bleach or some such that kills "99.99% of known germs dead", rather than just quickly rinse them or, $deity forbid, have gone directly from the cubicle/urinal to the hand dryer. That still leaves .01% [xkcd.com] to liberate and blow around. Per user.
    • My local movie theater has them and they remodeled in 2021. I had to tie my shoe and glanced up at one and it had mold growing in the bottom of it. I think I'll stick with paper towels. If we are worried about killing trees for paper towels, we can make them out of hemp.
  • The best thing about (Score:5, Informative)

    by ukoda ( 537183 ) on Friday February 02, 2024 @12:30AM (#64207578) Homepage
    The best thing about living alone is not being told how to leave the toilet seat on the assumption that only their opinion counts and they are right because of ... 'stuff'.
    • The best thing about living alone is not being told how to leave the toilet seat on the assumption that only their opinion counts and they are right because of ... 'stuff'.

      My SO and I had that discussion early on in marriage. I told her that If I had to raise and lower the seat, we were going to keep the lid down at all times other than for using the toilet. Works like a charm, and one less thing to worry about with children and pets.

      Some of her friends think it is sooo unfair though. The same friends that get pissed off that she makes me coffee in the morning. Come to think of it, those ones are all single and wondering where all the good men are. 8^P

    • Apart from that, you don't flush compost toilets. If you put the sawdust on top, the lid is obviously open. You close it afterwards (optional).
  • by TheMiddleRoad ( 1153113 ) on Friday February 02, 2024 @12:33AM (#64207580)

    They only measure right by the toilet and on the toilet. That's not what I care about. I care about my toothbrush that's 8 feet away. A lid down toilet will still spread close by, but it is less likely to spread far. An open potty is open season. This shitty study doesn't actually answer the question.

    • They only measure right by the toilet and on the toilet. That's not what I care about. I care about my toothbrush that's 8 feet away. A lid down toilet will still spread close by, but it is less likely to spread far. An open potty is open season. This shitty study doesn't actually answer the question.

      Bingo.

      With the lid down most of the airflow is reflected off the lid and directed down towards the floor where it's much less likely to spread higher up to counter level where a toothbrush is typically placed. It's also likely that there less contaminated air overall that escapes the bowl since the lid is an obvious barrier.

      With the lid up, though, it's free to swirl everywhere; as you said, "open season". No surface is safe, but at least with the lid down it seems like the spread would have to be more conf

      • When I got an electric toothbrush I realized there was no reason for it to be in the bathroom, since it didn't fit in the toothbrush holder, needed to be plugged in to recharge, and I don't need a sink for the first part of brushing. That's another 2 minutes I can spend shitposting on Slashdot!

        • Ditto. We keep ours in the kitchen, since there's a sink and outlet there too. I want to wet the brush since that makes it start so much better.

        • When I got an electric toothbrush I realized there was no reason for it to be in the bathroom, since it didn't fit in the toothbrush holder, needed to be plugged in to recharge, and I don't need a sink for the first part of brushing. That's another 2 minutes I can spend shitposting on Slashdot!

          A number of wives keep their electric toothbrush in a drawer by the bed.

      • by ukoda ( 537183 )
        Are you not making assumptions? Maybe the smaller gap increases the velocity of the air flow giving more range over a narrow band, straight to your toothbrush? Really it sounds like you need to get your hands on a supercomputer that normally does weather forecasting and change the model to match your bathroom. Next you need to verify the data from the model using florescence particles, UV lighting and a high speed camera, like they do when tracking a sneeze.

        Only then can you be sure of your assertions
        • Maybe the smaller gap increases the velocity of the air flow giving more range over a narrow band, straight to your toothbrush?

          Like I said, "...but at least with the lid down it seems like the spread would have to be more confined unless there are some very peculiar physics at work."

          Feel free to lick all the floors you want to confirm this theory.

        • The air is rushing around because of the water pouring in at the top and out the bottom, I would have thought that most of the air was being sucked into the bowl rather than forced out
          • by ukoda ( 537183 )
            You may be right but you are making assumptions too. Where is that supercomputer and high speed camera when you need it?
      • They only measure right by the toilet and on the toilet. That's not what I care about. I care about my toothbrush that's 8 feet away. A lid down toilet will still spread close by, but it is less likely to spread far. An open potty is open season. This shitty study doesn't actually answer the question.

        Bingo.

        With the lid down most of the airflow is reflected off the lid and directed down towards the floor where it's much less likely to spread higher up to counter level where a toothbrush is typically placed. It's also likely that there less contaminated air overall that escapes the bowl since the lid is an obvious barrier.

        With the lid up, though, it's free to swirl everywhere; as you said, "open season". No surface is safe, but at least with the lid down it seems like the spread would have to be more confined unless there are some very peculiar physics at work.

        You have to admit, for people who used to live among their shit, that now we are worried about the contamination when we flush it, I guess thats progress.

        It does raise the important question - Does fecal matter?

        • It does raise the important question - Does fecal matter?

          Only if urine the way when it splatters. lol

          • It does raise the important question - Does fecal matter?

            Only if urine the way when it splatters. lol

            Well played sir, well played indeed - you get a cymbal crash!

      • Mythbusters did this one years ago: https://www.youtube.com/watch?... [youtube.com]
    • by real_nickname ( 6922224 ) on Friday February 02, 2024 @01:55AM (#64207638)

      Wall contamination was minimal, regardless of lid position, and there was no significant difference in contamination level between the surfaces assessed,

      It's not the tooth brush position but it probably means your toothbrush is safe. Granted you don't breath your shit with a closed lid. They do have a toothbrush with a laser in their setup as seen in the video (you can see some particles flying near it in the open lid experiment) but I didn't see any mention in the paper unfortunately.

      • Wall contamination was minimal, regardless of lid position, and there was no significant difference in contamination level between the surfaces assessed,

        It's not the tooth brush position but it probably means your toothbrush is safe. Granted you don't breath your shit with a closed lid. They do have a toothbrush with a laser in their setup as seen in the video (you can see some particles flying near it in the open lid experiment) but I didn't see any mention in the paper unfortunately.

        I dunno about others, but my toothbrush gets washed before I use it. Maybe they can do a test on bounceback of the rinsewater from a washed toothbrush.

        Oh hell, I'm just shitposting at this point.

    • But how do you replace the taste?
    • by Samare ( 2779329 )

      No surprise there:

      Conflicts of interest: Drs. Julie McKinney and M. Khalid Ijaz are engaged in R&D at Reckitt Benckiser LLC. The other authors declare no competing interests.
      Funding/support: This study was funded by a grant to the University of Arizona from Reckitt Benckiser.

    • I was more concerned of the lack of first disinfecting the surrounding surfaces. How do they know when the contamination occurred there? Maybe a bad write-up.

      Also the result of the home test, with cistern, has no info on the result. Maybe the pressure of the water has a bearing on the result? I don't want to be that guy (or do I?) but did the people doing this experiment have a vested interested in the results they present, I could bet a dollar or two on that they were male.

      But on the other hand if the resu

      • by ukoda ( 537183 )
        Come on, have you not heard of gender equality? I for one defend the rights of women everywhere to pee with the toilet set up just like a man, should they so wish!
        • Come on, have you not heard of gender equality? I for one defend the rights of women everywhere to pee with the toilet set up just like a man, should they so wish!

          I learned very quickly in marriage that if she gets up in the middle of the night, and sits down right on the porcelain, she will come into contact with the water in the toilet, and you will hear about it for weeks. Can't say I blame them.

        • Absolutely.

          Now I assumed this article was of the lid, and furthermore just assume that everyone has the lid up when doing their toilet business. I may be wrong on both counts since I didn't bother to click on to the original article. But that doesn't make this article less unhelpful. (double negations, sweet double negations.)

    • by AmiMoJo ( 196126 )

      Why do so many countries combine the toilet, shower/bath, and wash basin into one room?

      In some places, like Japan, it's normal to have them in separate rooms. It doesn't take up much more space, you only need a thin wall and an extra door.

      Then again, our toilets are extremely primitive, basically unchanged since Victorian times, save for dual flush. Rimless models are starting to make some headway, but we still rely mostly on paper for cleaning ourselves. It's not like we don't know there is a better way, w

      • It's not like we don't know there is a better way, washlets exist and many people have seen them, you can even buy primitive versions on Amazon...

        After the great toilet paper shortage of 2020 I bought one of those add on bidets from Amazon. It takes some getting used to at first, but now I find using paper only to be kind of sketchy and would never go back.

    • I am sorry; the science is now conclusive. Any further work is disinformation.
    • Women: put the seat down!
      Men: put the lid down!
      Women: we did a study that proves that lids are the same as air!

      That's all that needs to be said.

      How embarrassing for the scientific method.

    • by vtTom ( 591066 )
      Mythbusters covered this very topic in one of their earliest seasons.

      https://en.wikipedia.org/wiki/... [wikipedia.org]

      tl;dr - "Fecal coliforms were indeed found on all the test brushes, including the control ones, but none at a level high enough to be dangerous."
    • by skam240 ( 789197 )

      Huh, do you really spend time thinking about this concern? While I'll admit the idea of a few fecal particles on my tooth brush is unappetizing there's little bits of shit on everything in this world.https://www.sciencefocus.com/science/is-there-really-poo-everywhere (and that article isn't even discussing insect and animal effects waste). Just give the toothbrush a little rinse under hot water before brushing and have at it. It's not as if there's ever been an epidemic of people getting sick from toilet ba

  • by Slashythenkilly ( 7027842 ) on Friday February 02, 2024 @12:38AM (#64207584)
    We spent millions and it helps keep the economy going and there is so much more we can find out! Do our pets "love" us? Does shoe size indicate IQ? Can an oreo cookie be twisted exactly in half? Is yawning contagious?
    • This particular study didn't seem to ask the question of whether or not the 'contamination' actually matters. Does it hurt or does it help? I for one like having an immune system and living in a bacteria free house is not going to help.

      • by La Gris ( 531858 )

        This particular study didn't seem to ask the question of whether or not the 'contamination' actually matters. Does it hurt or does it help? I for one like having an immune system and living in a bacteria free house is not going to help.

        Very good question!

        I remember in the 70's and early 80's it was common practice to have carpets with a special cut-out shape to fit the toilet base and sometimes even synthetic fur on the outside of the lid. This was obviously a trap for bacteria and particles. Another time with other rules.

        I feel no nostalgia for this overuse of carpeting in the wrong places, but fact is that we had no worse health, maybe even better health than nowadays. Possibly related to sane exposure to bacteria overall.

        • All the carpeted toilet seat does is delay the time it takes for a guy to realize he's peeing on a shut toilet seat - Al Bundy

    • We spent millions

      No one spent millions on this. Budgets for these kinds of experiments range in the thousands. But really? Just after a pandemic where we discovered how poor our bacterial dispersion modelling is and how little understanding we have of it, you think researching such things is a waste of time?

      I think we should do a study correlating the ignorance of Slashdot users with how high their UID is. You are an already damning datapoint.

      Stay in school kid, when you do your BS thesis you may just find the value of doin

    • by Dwedit ( 232252 )

      I love these images, it's a good test case for your content-aware fill tool/inpainting method of choice.

  • I know the toilet seat lids are not airtight nor can filter aerosols (I was surprised to find out that closing the lid makes no difference for the aerosol spreading, thoug). I would assume closing the lid still makes a difference for bigger drops of water ending up on the floor.
  • There is unlikely to be a reduction of microdroplets because toilet seat lids and toilet seats lack hermetic seals. Although it is quieter in the ambient area when closed. Edge case encountered: retrofit with a motion-activated bidet prevents flushing closed, but it eliminates the toilet seat up complaint.
  • except the ones who get their fecal on

    https://www.medicaldaily.com/y... [medicaldaily.com]

  • This is something I was actually thinking about a few times lately. Now I can refer to The Science, awesome.
  • ..when applicable. Less water used == less to be atomised.
    * On cisterns that have this feature
  • by tinkerton ( 199273 ) on Friday February 02, 2024 @06:48AM (#64207876)

    Measured by the smell that can linger afterwards it makes a big difference if you flush instantly after you dropped a big one and another time after sending all the paper after it, compared to only flushing once at the end.
    Just looking at what actually makes a difference here. Putting a flamethrower on the whole room is such a drag.

  • Physics can do some interesting things. As a microbiologist/Geneticists back in the 80s, I have ALWAYS closed the seat because it was shown that the germs were easily spread. Basically, ti was what we were taught. However, if this study is valid, it will be an interesting change.
  • by LazarusQLong ( 5486838 ) on Friday February 02, 2024 @09:45AM (#64208088)
    Looking at the pictures of the different plumes, it seems that the summary is incorrect, it appears that lid down creates a smaller plume.
  • And how horrible would said dispenser be on the flap valve and seals for the toilet over time? For myself, I doubt there's one that is low-odor enough that it wouldn't disturb my hyperosmia. I'll stick with cleaning my toilet regularly. I've made it to my sixth decade thus far.
  • by 0xG ( 712423 ) on Friday February 02, 2024 @01:54PM (#64208672)

    I had to say it. Sorry, I'll see myself out.

  • Change the design of the siphon to add only enough water, and make the flush handle activate a suction pump.
    This way you are not having bowl full of water to splash and swirl.

  • I wonder how much this study cost the taxpayers. More tax dollars flush down the drain.

  • It maters to the Toilet, will no one think about the toilet? #ToiletsMatter

  • it's more important that you remember to flush

Crazee Edeee, his prices are INSANE!!!

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