Saving The Planet One Flush At A Time

Toilet Sink Saves Water

Water is a natural resource that some of use humans take for granted. It seems that we can turn on a facet to find an unlimited supply. That’s not true in all parts of the world. In the US, toilets use 27% of household water requirements. That’s a lot of water to only be used once. The water filling the toilet after the flush is the same as that comes out of the sink. [gregory] thought it would make sense to combine toilet tank filling with hand washing as those two activities happen at the same time.

To accomplish this, a DIY sink and faucet were put in-line with the toilet tank fill supply. The first step was to make a new tank lid. [gregory] used particle board and admits it probably isn’t the best material, but it is what he had on hand. A hole was cut in the lid where a metal bowl is glued in. Holes were drilled in the bottom of the bowl so that water could drain down into the tank. The faucet is just standard copper tubing. The curve was bent by hand using a wire wrap method to keep it from kinking. The only remaining part was to connect the fill line (after the fill valve) to the faucet. Now, when the toilet is flushed, the faucet starts flowing.

Although [gregory’s] project may have increased the percentage of household water used by his toilet, it’s only due to the reduction of non-toilet related water usage. This water saving mod has inspired quite a few folks to make their own sink-toilet hybrid, check them out:

88 thoughts on “Saving The Planet One Flush At A Time

      1. I have always used only cold water to wash my hands. If you try to use hot water for that, you’ll waste a lot of water (and time!) in the process. You could install a mini hot water tank under the sink, except they’re disproportionately expensive for what they are.

      2. Two unfortunate points about Japan:
        1: the toilet faucet does not eliminate the need for a regular faucet for all those other needs. Do not real space savings.
        2: worse, most Japanese for not recognize the fact that its available for hand washing, or if they do, only to drizzle some water on their hands (mostly guys, no soap. Soap is so scarce in public toilets here).

        At best people put a scent/bowl cleaner block under it to make it somewhat useful.

        Oh, and most people don’t use the “small flush” either. :(

  1. The idea is not new but I really like it and have never seen it with toilet tank.

    There is only one drawback:
    The waste-pipes are designed in such a way that with a defined amount of water the solid parts of the waste (nice paraphrase huh? :p) can be transported, if we reduce the amount of water there is a risk that the pipe will block at some point (big problem with those waterless urinals).

    Anyhow, I don’t think that this should be a blocking point for those great ideas, instead we should make sure that our waste pipes (and the whole system) works with less water.

    1. I must have missed the bit where total water usage (for the flushing) is reduced. From what I understood, the same amount of water gets into the tank, only now it runs through the faucet/sink on the way – but it all ends up being available for the next flush…? The savings come from not having to run a *second* stream of water for washing your hands.

          1. It’s not about the waste pipe of the toilet. Its about the ones under the streets, the overall system.
            The central railway station here in Frankfurt/Germany is having massive problems as the waste is decomposed in the pipes and the gases find their way into the underground station leaving a special note.

            I don’t say that the invention presented here is causing this.
            I’m just saying that we should have in mind that especially older waste-systems are not designed to work with lower water quantities, its nice people care and we reduce our water consumption steadily but we should have the overall picture in mind which might be different for different locations of course.

      1. As Whatnot (and many more) have commented, I always thought this was a great idea for water-challenged places of the planet when I saw this solution in Japan over 20 years ago.

        Of course the other end of the japanese spectrum is heated toilet seats with water jets and starship enterprise control panels. And since japanese girls would tend to run the tap full-bore in order to mask any sounds that might be made during their visit, I’ve heard some even include speakers that will play the sound of running water, for even more water savings goodness! =)

      1. This does defeat the pressurized type of low flow toilet. (They store the flush water in a chamber that is pressurized to the supply line pressure (typically 80 psi in the U.S.)) The increased pressure on the flush water “shoves” a lot of solid waste out of the bowl and over the trap.

      1. Wouldn’t that tend to lead to microbial growth in the tank?

        Warm clean water, no problem.

        Cold gray water, probably OK.

        Warm gray water? That’s a recipe for problems! At the very least, you should put one of those slow-release chlorine tablets in the tank. I’m thinking a UV-C lamp in there might not be bad either, on a timer perhaps. Probably still a net resource savings, but I’d have to run the numbers.

      1. in Praha ‘(Prague) sometimes there is no water in the building for 2 days in very cold winter as water pipes breaks ( it’s -20C degree outthere and less , try Russia..) so yes water close to 0°C is really not good.

      1. Ah. I see.

        The system dumps the tank in the bowl and then flows more water in during the refill. My toilet doesn’t work that way. It’s just dumps a single load of water down and keeps flowing only for as long as you keep pressing the lever. The overflow tube is to the side and dumps water over only if the valve breaks.

        Doing the same for my toilet would empty the tank and then flow all the water down the sewer without filling the tank again.

  2. The whole water-saving thing makes sense in dry regions. Wasting whole rivers on growing fuel-corn sure is a horrible choice.
    But also here in Germany we have been educated to preserve water – although it constantly rains.
    As a result we got problems with the drainpipes, since they don’t get flushed properly anymore.

    1. I work for a water/wastewater department and i can verify that this is one hundered percent true of sewer systems. Using less water results in more build-up in the pipes. Any savings that the individual user had are completely negated by the wastewater crew that has to use a jetter to clean the pipes because of low flow. So you may save a few gallons personally, but many times that amount is used to remedy the ensuing problem.

    2. Exactly, here in the UK we get charged for sewerage on water consumption… yet the system NEEDS a flow of water to work correctly, as soon as you limit the flow, you end up ruining the way the system works…
      BUT ‘grey’ water should be used for things like flushing toilets, there is no need to use drinkable water to flush a toilet…

      1. the rubber seal over the flusher at the base of the cistern will degrade quicker. Whether the replacement cost/time of the seal is more than the amount of water saved will be the issue here.

        1. Not if I understand what I’ve read so far correctly. The water drains from the hand basin directly into the Overflow Tube, i.e. it bypasses the rubber/silicone seal of the flapper valve.

    1. These things are pretty standard in japan, but perhaps they have soap designed to work better with it though. Because your surface remark doesn’t seem unrealistic.

      On the plus side, you keep a fresh clean toilet from the soap.

    2. @NotArduino

      This bacteria you speak of colonizes everything in the home… especially the bathrooms. It helps keep harmful bacteria at low populations through competition. It actually makes the toilet bowl fairly “clean.” You know nothing in terms of micro-biology! Good Job!

      If you use liquid soap there will be very little scum. Maybe hackaday could get some for the comments section?

  3. I’d suggest a diverter valve on the top washbowl – there when/if you want to wash after flushing, but otherwise fills the tank without that column of water for kids and critters to frolic with. Can you tell we have cats?

  4. So the 1/2 litre or so of water this saves will save the planet? I’m afraid that’s nothing but a wet dream.

    AgroBiz and Industry burn thru BILLIONS of gallons every year, so that little drop of water you save is going to help how?

    There are many meaningful ways of actually saving the planets water, but this hippie treehugger crap is none of them.

    1. Sure it’s not an issue in many places, but did you hear about california? And vegas? And australia? And many other developed countries where they recently found they had water shortages.

      And the industry will continue to use their water, so to keep them and the population both in supply, it might help to try to preserve a bit.

      1. “It might help to try to preserve a bit”.

        Awwwwww, lets ignore basic math and go for the optimistic touchy-feely dreams.

        Consumers could cut back on 100% of their water use (which would be hard for most families) and that wouldn’t save enough water to be noticed over the evaporation rounding errors of the amount of water used by Industry and AgBiz.

        1. Fuck saving the planet, I’m in a county in USA where my sewage bill is 2-3x my water bill. I literally pay an average of 180$ monthly for power and 150$ for water(~40$) and sewage(~110$). This could potentially save me a lot of money on sewage, not a bad hack for where I live.

          1. Nope, they typically bill sewage based on your water usage; figuring most water you use will go down the drain.

            Of course, if you water your lawn, you’re getting charged for sewer use despite not actually using it. And collection of rainwater is typically made illegal as well, because you might put it down the sewer; and they’d have no way to detect that or bill you for it.

          2. Wow your ignorance must be blissful. The gov rarely builds or maintains anything they are just a middle man that gets to take a portion of your hard earned money.

            “BUT WHO WILL BUILD THE ROADS????” The ignorant dolt says. Private contractors build the roads and infrastructure and often times with less competition because someone is related to a bureaucrat or in the good ol’ boys club. Not to mention the tax exemption on municipal bond interest further reducing competition and driving up cost.

            According to your wikipedia:
            It’s so obvious the problem isn’t a privatized sewer system, it was bureaucrat’s gambling with municipalities bond swaps because they were bribed by wall-street and would be out of office before the proverbial “shit hit the fan/pipe.” Can you be any more delusional?

   Please respond and tell me how stupid I am for wanting more competition and removal of market destroying subsidies. And ultimately how the great and all-knowing government does it better and they could provide utopia if only they would raise taxes and require slave labor to build your precious infrastructure while somehow excluding you from being lumped in with the other wage-slaves.

          3. In response to Chris C.s comment, our community (far from California) has allowed people with private wells to connect to municipal water and sewage. The well must then be disconnected from the household supply, but the owners are free to use the well for lawn and garden watering, and car/house washing.

    2. “AgroBiz and Industry burn thru BILLIONS of gallons every year, so that little drop of water you save is going to help how?”

      If/when water supplies become expensive, Agriculture and Industry will scale back as well. Such as the Arizona orange growers that went out of business leaving fruit to shrivel on the trees when their water sources were diverted to municipalities.

      1. To me it reads like the real problem there was try to grow oranges in Arizona. Sounds as stupid as growing irrigated corn on the Kansas High Plains where it needs irrigation rather leaving the corn production to the Midwest where their is sufficient rainfall most years, up to this pont anyway

        1. Yep! But until the population in Arizona grew large enough to use the water, the land was cheap and the water was cheap (snow runoff from the Colorado Rockies into Lake Mead). and the temperatures were right.

    3. A1/2 liter saved multiplied how many times that amount is save can extend the life of an area’s water source. While they damn near waited until the point of no return A gricultur has reduced the amount of water it uses.. Same for many industrial users if wter

  5. If fresh clean water is short in demand in certain parts of the world, how would they get more if I use less?
    Here, they have to pump fresh water in to the sewer plant to dillute the incoming waste-water, since people has started to use toilets with smaller tanks an shower nossles with less flow..

    We got plenty of fresh water, and it’s not like the dry villages of Africa will get more of it if I use less

    1. The “fresh” water pumped into your sewage treatment plant probably does not have to be processed as much as the water you drink. I imagine it is not chlorinated or fluorinated, maybe filtered to prevent sediment from building up in the supply pipes.

  6. That little basin… water allover the particle board… There should be at least a basin covering the whole top of the tank, but it wouldn’t be deep enough. There will be water splashed on the seat… weather it’s up or down. Who wants to sit down now?
    A sink for handwashing has to be big to contain the mess of water made with it in your hands.
    Get rid of bar soap! Bacteria can grow on it, it’s always dirty with the last users yuck on it. Sink and such left clean after use.

  7. This is really an issue in what refers to a monthly water fee, so for me what i have think of is a tank to fill with wasted water like hand wash, and also bath waters.. because specially bath wastes a lot of water, it depends from person to person but i would say somenone that baths one time a day, would get enough water to flush the toilet for an entire day of usage, so… this for me would be a really water saving system.. and of course, redirecting washed hands water to that tank would help just a litle… This trick i bet it could reduce monthly water costs to half, but it takes the space to make the system and it can have a not so clean look..

    For the model presented in the topic what happens if you wash your hands every hour and you only flush toilet once a day? would it leak from top? hum…

    1. Doesn’t it stand to reason if you flushed once a day, you would only be using the wash basin once a day as well. Besides any excess water will go down the bowl fill/over flow tube before it reached the top of the tank.

  8. Here in Germany we sometimes had an silly problem with to less water usage…
    it was because a huge residential zone had to much empty flats but it is also a problem if to much water is being safed:
    The water was standing in the pipes and started to breed bacteria because of to small through flow…
    …the fixed the problem with opening firefighter hydrants from time to time to flush the pipes

  9. I’m a guy, I live alone, so I pee in the shower and the toilet tank to save water. I’m so green it makes Al Gore ‘moist’. Seriously, there is a simple rule and I know plenty of people on septic systems that follow it. “If it is yellow, let it mellow. If it is brown, flush it down”.

    1. I’m male live alone. Depend on a private water well and a septic system, but I rarely leave it yellow; nothing worse that a plosive crap slashing that yellow on your junk and , butt. I rural so I can piss outside. A properly constructed and maintain septic system should be able to handle the yellow flushes.

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