Introduction: Save (a Little) Water With a 3D Printed Toilet Sink!

Picture of Save (a Little) Water With a 3D Printed Toilet Sink!

Not long ago I saw an instructable on hacking a toilet for free water and I wanted to see if I could make my own version using my 3D printer.

In summary, a 'toilet sink' is just a simple plumbing hack that lets you wash your hands with the fresh water a toilet uses to flush. In this way it can reduce your water consumption by eliminating the need to use even more water to wash your hands. The toilet sink also has the benefit of helping keep your toilet bowl clean!

This instructable will show you how to make a 3D printed toilet sink and make it waterproof, even if you did a horrible job printing it!

Step 1: How Much Water Does It Save?

Picture of How Much Water Does It Save?

To save myself a bunch of grief in the comments section I'll go ahead and immediately point out that there are much better methods of saving water than this. To quantify that, I did a little experiment to estimate how much water this thing can save.

I measured that I use about 4 cups of water to wash my hands in a normal sink. If I normally flush the toilet 5 times in a day every day for a year then I'll consume 456 gallons per year. Sounds like a lot but how much water is that is practical terms?

A typical American adult uses between 80-100 gallons of water per day. The average price of water in the United States is about $1.50 for 1,000 gallons, and you can expect to pay essentially the same amount for sewer costs. So that 456 gallons translates into a savings of $1.37 per year. (Californians can triple that.)

My toilet sink probably cost me about $20 in materials, so I'm looking at a 14.6 year payback period...

Clearly the primary benefits here are the novelty, the cleaner toilet bowl (from your hand soap), and knowing you've reduced your water consumption by some degree.

Step 2: Improvements to Original Design

Picture of Improvements to Original Design

Again you can see the original design here. Here are the primary things I've done to differentiate my design.

1. Obviously mine is 3D printed so the design is much more repeatable & easily shareable.

2. Instead of a plywood tank lid I used a shelf. The shelf was great because it looked better, it already the correct dimensions, and the outer surface is more water resistant.

3. Rather than dumping the used grey water into the tank I dumped it back into the overflow tube where it was intended to go. Dumping that water into the tank would likely leave behind a scum buildup over time.

Step 3: Parts List

Picture of Parts List

(2) Printed Basin Halves

(1) Printed Faucet

(1) Board or a wall shelf that will fit your toilet tank

(1) Nylon Hose Barb 1/2" NPT and for 1/2" ID tube

(1) 3' of 1/4" ID vinyl tube

(1) 1' of 1/2" ID vinyl tube

(I've provided the model files in case you don't like my simple square design. The format is from Cubify Design.)

Step 4: Repair & Waterproof the 3D Printed Parts

Picture of Repair & Waterproof the 3D Printed Parts

Long story short my print settings were messed up so I ended up having major warping issues on the parts. (I didn't want to waste them after 8 hours of printing either.) That's OK though because you can easily repair parts using a thick slurry of ABS glue (Acetone + ABS scraps). Just spread it on with a putty knife and let it dry. The result will be a smooth waterproof surface.

Step 5: Glue the Parts Together

Picture of Glue the Parts Together

Use the ABS glue to bond everything together. Try to minimize the lumps at the seams because the paint wont hide them!

Step 6: Sand & Paint the Assembled Parts

Picture of Sand & Paint the Assembled Parts

Now that it is completely dry use a razor and sandpaper to scrape off the lumps as much as possible. Then I used a sandable filler primer to prime the plastic and to help fill up any small cracks. After that dries you have to sand it again and dust it off before painting it.

Step 7: Assemble Components

Picture of Assemble Components

Cut the hose barb shorter so that it wont stick up inside the sink basin. Then screw it into the bottom of the printed basin and put hot glue around it to ensure that it is waterproof. After it cools you can attach the drain tube. The fresh water will come through the small hose which is run all the way through the faucet up to the top.

Step 8: Install

Picture of Install

Connect the tubes as shown in the pictures. The fresh water comes from the pressurized refill tube. Just make sure you clean the connections really good.

The sink drain is pushed into the overflow pipe. When you flush the soapy sink water dumps directly into the rim of the toilet. You will notice that your toilet water becomes sudsy every time you flush. I'm counting on this to help keep my toilet bowls clean!

Step 9: Other Ways to Save Water

One of the major positives about the toilet sink design is that it doesn't require the user to change their lifestyle to save water. This is important because many of us won't take the environmentally friendly route unless its easy and doesn't require us to change our habits (i.e. there are many people who won't to let their lawn die to save water. For the record, I would).

Water is really cheap but that doesn't mean we should be wasteful! Here are a few water saving tips that don't involve major changes to your lifestyle.


1. Get a front-loading washing machine, which use ~60% less water than a top-loader (~30 gal/load saved) . (Front-loaders cost about $100 more than top-loaders, but common savings are $100/yr primarily from the reduced hot water consumption.)

2. Use a low-flow shower head (1.5 gal/min) rather than a standard one (2.5 gal/min) and save around 3,000 gallons per year per person (saves about $9/year in water and a lot more in heating energy).

3. Using a low flow toilet (1.28 gal/flush) instead of an older model (4 gal/flush) can save 10,000+ gallons per year per person (saves about $32/year).

4. Get a water conserving dishwasher, which use ~30% less water than a conventional one (~3 gal/ load saved)

5. Repair leaky faucets. (Unquantifiable savings)

6. Insulate your hot water pipes so you don't have to run the shower/sink as long to draw hot water. (Unquantifiable savings)

7. Buy a professional pre-made toilet sink, brand name 'sinkpositive'.


What are your favorite no-lifestyle-change water saving tips & tools? Let me know and a be sure to vote for this project in the Instructables Remix 2.0 Contest!


RuchamPsaJ (author)2016-05-22

why does she have a toilet? everybody knows that women don't use it lmao

Phil_S (author)2015-09-17

Saving $1.37 a year? Wouldn't buy a bottle of beer.

"Grey water" reuse has been around a while as has the combined sink/WC, mainly to conserve space. Grey water gets properly stinky if left around for a few days and the whole idea of the flushing water closet was to do away with such nastiness.

There might be some issues with potential cross-contamination of water supplies depending how you are plumbed.

As a water engineer, I applaud anything that conserves highly purified drinking water, for many reasons. Who the hell needs to flush cr*p with drinking water?

On the whole, people wash themselves and things far too much. 100-gallons a day? That's 33 builders buckets full or nearly 500-litres or half a tonne of water. I come from a generation when Sunday was washing night, Dad first, Mum next, me last, one tub.

Here's my formula for water saving. Potable water for drinking and cooking only - that cuts water use to 20-litres or 4 gallons a day per person. Everything else uses rainwater, soft, free water, loads of benefits. Keep a compost heap. Pee is loaded with nitrogen, put it on the compost. Now for the really shocking bit. Use one of those builders buckets plus some sawdust for "solids". Get over the flushing thing, learn to love it. Centuries of societies have valued "black soil", midden pits, even the most advanced waste water (sewage) treatment plant recycle the solids as soil conditioners and treated liquids to return to streams and eventually drinking water.

However - you might need a very understanding partner to share your habits.

barnabas09 (author)Phil_S2015-11-12

Sharing habits with an understanding partner is not always your own thing and be and let live...freedom is more important than approval.

gravityisweak (author)2015-09-10

Those who aren't interested in this for saving water could just put a decorative fountain there instead. Still the same concept, still pretty cool. If you were really in it for some serious water saving, you could convert your toilet to use collected rainwater to flush, instead of treated potable water. Anway, cool instructable!

Uncle Sam won't let you collect rainwater. Look it up.

I did look it is NOT have the RIGHT to collect rainwater

and don't let anyone tell you otherwise

gorozco (author)barnabas092015-11-12

People have been collecting and using rainwater for everything from gardening to washing their hair since long before you were born. Pretty sure it's not illegal anywhere, though the water sadly is not as clean and safe as it used to be.

gorozco (author)ThisIsMyNameOK2015-11-12

In Colorado is not permitted "unless you own a specific type of exempt well permit", I remember some other states have similar laws, is not Federal.

gorozco (author)gorozco2015-11-12

Other states that have rainwater collection laws on the books include Arizona, Illinois, North Carolina, Ohio, Oklahoma, Rhode Island, Texas, Utah, Virginia and Washington.

That's an urban legend that's been circulating. It's legal in all 50 states. Only Colorado has any restrictions.

Well, my uncle Sam won't let me use his barrels to do it. He is using them for nefarious purposes.

While it would be a good idea to check your local regulations beforehand, just in case, that is largely untrue.

Lol a toilet fountain, I love it!

There is already an Instructable for making a toilet fountain. I can't remember who was the author, but you can look it up. :-)

Toilet fountain for the win.

Running the idea by the lady of the house now.

JennaSys (author)2015-09-17

I'm not sure if it's an issue in practice, but this design could be considered a little unsanitary. Toilet bowls are glazed making it easier to clean and more difficult for bacteria colonies to take hold and grow. The inside of the most holding tanks I've seen is quite porous and could turn into a bacterial breeding ground for what is being washed off of your hands. I supposed one solution for this would be to have something like a chlorine or other chemical treatment in the tank itself, but it probably wouldn't work 100% and while you may be saving water you are adding more chemicals to the water supply which will take some amount of energy to remove down the line.

ThisIsMyNameOK (author)JennaSys2015-09-28

You may have a valid concern. I know there is currently some nasty stuff living in my toilet tank (very old toilet, has not been properly maintained).

However, if I am understanding this correctly, the water drains from the sink directly into the toilet bowl, bypassing the tank....

"When you flush, the soapy sink water dumps directly into the rim of the toilet" (step 8)

JennaSys (author)ThisIsMyNameOK2015-09-28

You're right I missed that. It looks like the drain from the sink is made to go right into the overflow tube and not into the tank itself, and as such it's not as much of a concern. So in that case, carry on!

TracerElements (author)JennaSys2015-09-17

JS Would glazing the inside of the toilet tank make better sense all around?

JennaSys (author)TracerElements2015-09-17

Possibly, but I think the glazing is usually put on as part the porcelain firing process so it might not be possible to get the same effect. There may be other coatings you can use (spray or brush-on) that won't be as effective, but may be a good compromise.

miked2001 (author)JennaSys2015-09-22

Epoxy, they do that in boats to seal the water tanks.

You just dont get it do you? You talk about the benefits of a porcelain glazing without even knowing it's properties and limitiations. Even a pure industrial grade ceramic coating (as being experimented with in Japan for their urinals) won't stop bacteria because the coating itself would have to be "antibacterial" and COMPLETELY FRICTIONLESS TO THE BACTERIA so they have no ability to take hold, and humans do not yet possess the knowledge to make something that smooth. If you don't know what I mean by frictionless - look it up.

@ Jennasys - How can the inside of a holding tank be "porous"? do you even know what that word means? Glazed to make easier to clean, yes - glazed to reduce growth of bacterial colonies? no frikken way - bacteria are microscopic and the glazing is NOT SMOOTH - to a bacteria the surface of the glazing looks like the himalayan mountain range, plenty of places to nestle and grow. If a toilet is being flushed several times per day, the water from your washed hands is ALSO being recycled several times a day, leaving little time for the "bacterial breeding ground" you are speaking of. PLUS the water from your washed hands is GOING DOWN THE TOILET!!! NOT BEING USED FOR ANYTHING OTHER THAN WASHING s*** AWAY!! so it matters little if it is contaminated with a few hours worth of bacteria, as it's about to enter the public sewers and get a whole lot worse. geez ppl THINK a little.

No need to yell austin.hall, I really don't care about it that much. I was just considering the fact that I can wipe down a glazed surface and it will be relatively dry compared to trying to wipe down one that is unglazed which has moisture absorbed past the top surface. And you are correct in that bacteria can certainly grow on a glazed surface which is why a toilet bowl requires regular cleaning. A tank does not require regular cleaning however because it is sanitary (physically separated from the contaminated water), and if it did need to be cleaned it would be very difficult to do so because it is NOT glazed. That's all the opinion I have on it, so from here on out I'll defer others to your expertise in the matter.

ThisIsMyNameOK (author)2015-09-28

Interesting, if not the most practical way to save water. It's a conversation piece anyway, and a unique decorative touch in the bathroom.

On the subject of ways to save water, you can create your own low flow toilet by filling a 2 litre pop bottle, or similar container, with water and submerging it in your tank, so that every time it fills it uses 2 litres less water. You just have to be careful to make sure you still have enough force in your flush so that your pipes don't clog.

miked2001 (author)2015-09-22

Man oh man, some people just cannot say, "Cool Idea, it may not work for me but I love the direction." Hence, Cool idea, I love the thinking here.

I am on a well and in the summer it is always at risk of running dry, which it has more than once. I cringe when I see people brushing their teeth with the water constantly running, or doing dishes with the never ending water fall, etc. My only concern is the soaping of the storage tank and any issues it may cause on the seals and other mechanisms. Marvelous thinking here my boy, keep it up.

P.S. in Aruba and on other Caribbean islands they use shower, sink and laundry water to flush the toilets and water the lawns. This is right up the same alley.

ThisIsMyNameOK (author)miked20012015-09-28

I had the same concern about the soap in the tank, but after reading a little further, it looks like the soap goes directly into the bowl, not into the tank.

I also cringe when people run water unnecessarily. I love the idea of using grey water and think it should be adopted everywhere.

gbrajovic (author)2015-09-25

Consider that the water savings will be more than enough to keep some pots with veggies, without adding to your current "water print". Very nice idea.

dlewisa (author)2015-09-22

I've always wondered about a flushless urinal that would be "flushed" by the water from washing your hands in a nearby sink. A kind of gravity flush.

Ginko Balboa (author)2015-09-22

Sir, you are a GENIUS!

MatthewJ20 (author)2015-09-22


alzie (author)2015-09-19

I save water @ home by yellow listing myself.

No need to wash after a pee.

Its clean, i washed it this morning any way.

nathanaloysiusbash (author)2015-09-18

It could save water to design a gravity fed greywater system, where the cleanest water is used at the top level of a home and then gravity fed down for greyer and greyer uses. If a person had the option of multiple drains, one drain for reusable water and another for too dirty water. Even rainwater could be used. When not collected off a dirty roof, it is more than drinkable. Cleanly collected rain is much better tasting than tap water where I live. For some reason, perhaps dissolved gases, plants respond better to rain water than city. Water that sits stagnant in tanks can develop odors but a small amount of bleach or another method such as heat to stop growth of microorganisms would keep water from smelling. I dont know why cities have developed towards centralized water distribution rather than wells. In many cities drilling a well is illegal within city limits. It is baffling.

They do it because then you're getting your water FOR FREE. They don't like that.

It is a shame but that is what I think too. No where is there a place where life is free. Even when you own a home or land, still you are just renting at a lower cost from the government. If you dont continue to earn money to pay taxes, the property can be taken from you, making you homeless. Even to camp at that point without paying money is a crime. Basically not having money or leeching off someone who has money is illegal. We must all contribute to society by making sandwiches and scrubbing the toilets of rich people. If they had to do it themselves, the whole world would explode.

Miam2004 (author)2015-09-18

this toilet sink seems discusting. i dont think that this should have ever happend bc its really discusting

@ Miam2004 You SERIOUSLY need to get out and see more of the world if this disgusts you. Not only is this a cool idea, it's practical, has no harmful effects and if every single flushing toilet of this type everywhere in the world did it, it would reduce the water requirement for the entire world by quite margin. - Think about the fact that the city of Las Vegas in USA has thousands upon thousands of toilets in hotels, yet the only source of water is the colorado river reservoir that has lost 10% of it's volume in the last 50 years. In a world where DRINKABLE WATER (which is what the water going to your toilet is, yes it's the same stuff that comes out of your tap in the kitchen that you drink and wash your food in..) is used to flush away waste, anything to reduce how much is wasted is a GOOD THING.#moronswillhatebecausetheyarestupidandjustdontgetit

nathanaloysiusbash (author)2015-09-18

very good idea. Nicely done. To me Flush toilets are accepted as normal,something we cant do without but they waste a lot of water and can create health problems later on from sewage pollution. A simple hole dug in the ground, just a small hole made with a garden trowel then covered with that small amount of dirt would suffice, no odor ,no massive sewage problem, a much more natural squatting posture, and the avoidance of the cooties spread by communal use of the toilet. It's just not what people are accustomed to.

Yess....the conventional commode wastes water and pollutes the environment...much to the dismay of enviro people...soo ...what is the alternative....detoxity organic food only ....create a compost pile....use a

barnabas09 (author)barnabas092015-09-18

5 gal bucket....spray yourself and irrigate your self....spray the results to make them liquidy....pour upon said compost pile...voila... you are now a citizen of planet earth rather than planet Europa....get a life and more abundantly

barnabas09 (author)barnabas092015-09-18

Just watch out for the neighbors and the police....they will push you down into their septic tanks

TracerElements (author)2015-09-17

Thanks JS... I just thought it made more sense esp. with the water we have around here. Tends to leave a certain hue in the toilet bowl, glazed or not.

jimvandamme (author)2015-09-17

If it's yellow let it mellow.

If it's brown, flush it down.

knottybeader (author)2015-09-17

Couldn't you put an overflow valve in the holding tank so the grey water collects until you're ready to use the stool? If the grey water in the holding tank reaches the overflow valve it would either drain off or automatically flush. Great space saver and conservation effort! Thanks!

Graham Leach (author)2015-09-17

Nice hack. The japanese go there first though. Here's some of their related work:

Crotus2k (author)2015-09-17

I really like the cherub idea. AND...of the cherub could be printed so that you could turn him slightly, it could be a hilarious prank. When you are finished with the facilities and flushed, wait for the water to stop and turn the cherub to the front facing position. The next flusher will either see the little devil also releasing into the toilet, or (if one is foolish enough to be seated when flushing, get a refreshing spray on the back, head, etc.

danallen82 (author)2015-09-17

This is how they do in Japan, where water and space is hard to come by. Its a really good idea, Americans are stuck in a wasteful mindset. It won't be long before water is the most expensive utility. I applaud you for your effort.

rippa700 (author)2015-09-17

This is one of those obvious saving devices that we have all missed. Brilliant, and I'm ashamed not to have thought of it. Great concept with or without the 3d printer - well done!

About This Instructable



Bio: Hi I'm Michael! I'm a dog owner, husband, writer, and mechanical engineer and I love getting my hands dirty building stuff. If you ... More »
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