I Made a Toilet Tank Sink!




Introduction: I Made a Toilet Tank Sink!

About: We are Mike and Lauren. We make videos on YouTube about money, travel, homesteading, and DIY.

I made a sink that goes on top of your toilet. When you flush, the fill water is re-routed to a faucet (don't worry, it's perfectly clean). Wash your hands like normal, then watch the water drain directly into the toilet tank. Next time you use the bathroom, the recycled water flushes the toilet and clean water is dispensed from the faucet. The design saves an estimated 1 gallon of water per person, per day! No modifications are made to the toilet except for routing the fill water tube into the bottom of the faucet.

Step 1: Design

I saw this idea a long time ago when looking into Japanese toilet technology. I finally decided to make my own out of concrete. I used sketchup to get the dimensions, then made a mold of my tank lid using silicone rubber. The shelf shape was inspired by JON-A-TRON's instructable.

Step 2: Experimenting With the Form.

I wasn't sure if you could just press a sink shape into wet concrete, so I didn't have high hopes for this first pour. I used Quikrete countertop mix.

Step 3: Air Bubbles.

I quickly learned that air bubbles need somewhere to go when you pour concrete. Whoops. Otherwise the it set up nicely and was really strong.

Step 4: Grind. Fill. Polish.

After grinding the air bubbles mostly out, I used Henry's feather finish to fill all the holes. Then I sanded down to 400 grit before finishing with a concrete water sealant.

Step 5: Plumbing.

The plumbing for this project was really simple. Just hook up that black tube that normally fills your tank into the bottom of the faucet. I used an assortment of brass fittings to go from 3/16 barb to 3/8 thread.

Step 6: Finished.

I'm thrilled with the finished product. The concrete looks great and it's extremely functional. You have lots of time to wash your hands after flushing so there's no rush.



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    18 Discussions

    Nice! The water should slowly polish the sink and make it super smooth :)

    Let me see if I understood:

    You wash your hands.

    The water from washing your hands goes to the tank.

    You flush the toilet.

    Water that's in the tank (that came from the sink) goes into the toilet.

    That water goes into the sewer.


    6 replies

    I think it's the other way around: the tank water is syphoned UP into
    the tap then dropped back into the tank after washing your hands. This
    is why the creator spoke about his friends hesitating about using water
    "from the toilet tank" which is understandable (the hesitating) though
    unjustified. I guess the hesitation comes from not being able to wash
    the insides of the toilet tank, and the fact that the inside of a toilet
    tank is matt, so easily invaded by germs, and not available for daily

    Nope. It's fresh water from the water line. The water in the tank is used for the primary flush.

    Actually, the fresh water should never touch the inside of the tank. If you look at you float valve in your tank theres a small plastic tube coming from it and clips on to the overflow tube. This water is as clean as what comes out of your tap. In this instructable the designer runs the tube to the faucet. Then it looks like waste water then drains to the tank. Its not clear if the waste water goes into the tank or into the overflow tube. Being that plumbing was my trade for a number of years, i would think it would need to drain to the overflow tube. This is what fills the bowl back up. The tank will fill from the small holes at the bottom the float valve. It appears that when you flush the toilet the faucet will automatically run when the float valve is opened giving you just enough time to quickly wash your hands as the tank refills. Hats off to the creator on the design and craftsmanship. Very nice instructable!

    I see now, and I am rightly corrected! Thanks! I love the idea and the way it is exposed.

    I see... And I have to admit that it is kind of disgusting! :)

    No, you had it right. Hand washing is hygienic. The tank water is gray water from hand washing, and next flushing uses that water.

    The other commenter was the one which was "incorrect".

    this is awesome :) and a good way to save water and space

    Very cool! Love this idea - good job!

    After reading the comments I see that there are people who do not understand how the plumbing in this works. After flushing, the clean drinking water that comes from the water line connected to the back of the toilet flows out of the top faucet (same water as your kitchen sink) this cleans your hands and falls into the top tank of the toilet. Then the next time you flush, the hand washing water that was stored in the top tank drops down to flush the lower toilet bowl. Completely heigenic!

    1 reply

    Thanks for helping me to understand. In fact it works exactly like the new French system in recent blocks of flats, but unfortunately not all of them!

    Great idea!!

    That is brilliant. You're lucky to live in America where you can get those DIY products, and clever to try your hand with them successfully. In France we can find little sinks on top of toilets in the most recent flats and houses: their use is upside down to yours; you wash your hands and the soapy water is collected in the tank ready for flushing with. Same difference, but this way you don't get the hesitations about using water that has sat in the actual TANK for some time (I agree this water is clean, but somehow I understand people's hesitations. These may come from the fact that there are blue salt lumps you can place in the tank...? The closeness of the tank water to the drain...? The fact that people don't clean the inside of the tank...? Anyway, thanks for that!!!

    1 reply

    The handwashing water comes from the house's main water line (pressurized) not the tank.

    This is awesome, an excellent way to save water

    Well done! I like your use of concrete. This project not only will last a long time, it will also save you money.


    1 year ago

    I like that idea. I can see somebody marketing such a device to help save on water. Sinks that drain into tolet tanks to reuse for flushing is a great idea. Thumbs up!

    This is just so brilliantly commonsense that it must be against all plumbing codes. ☺