Picture of Hack a Toilet for free water.
This Instructable is a step by step description of the process of adding a sink to the top of a toilet allowing the use of the clean water before it goes into the bowl.

Water is a precious resource and our everyday lives are immersed in consuming it. The average toilet uses excessive amounts of water. This hack allows you to minimize some of that water consumption.
I wanted this instructable to be simple enough that anyone could build it with basic tools and materials. I also tried to be material conscious with this project in that: many of the materials are recycled from other things (sheet wood and copper tubing) or second hand (metal bowl), and that it is put together using screws and friction fittings so when the sink has finished serving its purpose it can easily be taken apart and the parts can be recycled.

Step 1: Materials

Picture of Materials

9inchx20inch piece of sheet wood
Small plastic funnel
Copper tubing half inch outside diameter
Metal bowl approximately 8 inch diameter
4 feet of Vinyl tubing 1/8 inch inside diameter
4 "L" brackets and small wood screws
Scrap paper
Silicone latex caulking glue
Steel binding wire

Hand drill
Jig saw
1/2inch spade drill bit
1/8inch drill bit
Center punch
Hole saw 3 inch
Exacto knife
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TravisL716 days ago
Why has no one pointed out that, unless someone else is paying your water bill, there is nothing free about it?

Instead of having to flush the toilet to use it, why not make a water switch that pushes down on the valve to tun it on anytime? You also don't need to worry about where the drain is. The bowl drain can fill up the water tank to the overflow if the level is set lower.

In the picture below the Phillips screw top can be pressed down to run the water. A wooden cam knob could hold it down when turned any time. Not just when flushed, thus saving more water if the tank level is lower than the overflow. Then you are actually using the water twice, not saving any. Any water going into the overflow is not actually saved either.


Even simpler, adjust the float so it doesn't fill the tank completely after flushing. The extra volume freed up can handle the drainage from the sink.

Makes sense! Great idea.
diy_bloke2 months ago

another solution that I have seen with urinals is that the drainpipe of the basin, immediately streams into the urinal to flush it

This is a great Idea but I would consider using higher grade wood that has been sealed with polyurethane or another water resistant coating. With the sink and the toilet bowl on and under the wood, it's eventually going to get wet. It won't take long for it to start to separate, mold and/or hold in bacteria.

Madren6 months ago
Honda Enoch2 years ago
Ok, here are a few comments and questions I have.

1) What if you only need to wash your hands, like before eating. Flushing to activate the "sink" would be wasting more water then your saving.

2) We conserve water by following the "if it's yellow let it mellow. If it's brown, flush it down" rule. The toilet is only flushed 2-3 times a day rather then after every use. No it does not stink.

Just some thoughts.
I would just use hand sanitizer if just needing clean hands. I would also pee outdoors if conserving that much water.

Yes it does stink as you get older but so what . good saying

Actually I thought about this as well and I figured out that you could do two things to solve this problem:

1) Carefully notch the lid and run the faucet hose to a tee attached to the tank inlet hose.

2) Instead of using a simple pipe install one of the levered water dispensers you see on kitchen sinks. The kind that have a definitive on and off not just a momentary press.

Doing these things in addition the to sink install would give you a sink you could use all the time. For extra points notch and carefully drill the original ceramic lid for a true bathroom look. (The basic idea behind drilling ceramics: http://ds5.org/4039 )

Failing that they now sell these: http://sinkpositive.com/web/

But where's the fun in that! ;-)
Jails have been doing this for years. We did some construction work for the jail here. The top is a water fountain so you can drink, It flows into the sink on top the "tank". When you flush, it activates that as well to flush and fill the "tank".

This is a good way to help save water. Great project.

Nice idea. FYI, in the plumbing and green building trades, this is referred to as grey water. Some buildings collect drain water from sinks in big tanks and after filtering it a bit, use that as the water to flush the toilets or for irrigation.

Akin Yildiz7 months ago

so exciting to see how many people have copied your work and all the comments. this is such a cool hack.! thanks for sharing

Yong20107 months ago

Whoo Aha~!

What a genius!

This is that I have been looking for.

Thanks for the idea.

ironsmiter8 months ago
Since Hackaday revived this 'ible, I thought it a good time to revisit, reread, and comment.

If renovating a bathroom, or designing a new one, my main complaint about this idea could be easily solved. That is, you have to straddle the bowl to use it! In building new/remodeling you could have the toilet rotated 90 degrees, on a kneewall and be able to stand on the side of, or behind the tank. Much closer to the sink portion.

There aee a few comments about wasred water and...well, top mount dual flush valves would mitigate that, AND make JUST washing your hands 'waste' less water without having to rig a seperate faucet valve.
Having grey water sitting in the tank may not be the best for the plumbing parts, so occasionally dosing with bleach or other scum remover will be required, and keep an eye on the plastic and rubber parts for leaks; especially the rubber flapper.
Flash6710 months ago
I'm curious, can you drink the water?
AllenS1 Flash679 months ago

Technically, yes. The water that goes into the back tank of a toilet comes from the same place water at the sink comes from.

I haven't looked at the materials list close enough to see if there wouldn't be any contaminants from that, though...

John Nosh1 year ago

This is such a nice post thank you !!

I installed a french suspended model "WiCi" from www.toilet-with-sink.com last year. Quite expensive but works fine. So for my other toilet I will try to build one by myself like you explain !

etcmn1 year ago

Thanks. I'd seen these and figured I could build one for a fraction what they cost. Always nice to find someone has saved me time by having done the design work for me. :)

P-FANTASTIC made it!1 year ago

Thanks for the awesome idea, man! My bathroom doesn't have a sink, but with your instructions, I was able to make one.

thessejway1 year ago
Curious about the overflow idea.
If you want to save water use wouldn't the extra... soapy water go back into the tank. Are you actually saving water or simply making use of the water source. If you don't have a sink this is great. I wonder if it is possible to reuse the "grey" water for the next flush?
Excellent instructable! Off the shelf alternatives are so much more expensive (e.g. SinkPositive or the Caroma 305)... so followed this general DIY with a few adjustments and only spending $15 in basic parts and made the version shown in photo. Used a temporary plastic cover, as shown, but will likely drill directly into the original porcelain lid to make it look nicer. Thanks so much to gregorylavoie!
Just what I needed. Now let's see if I can convince my ever cautious DH. Thanks for sharing.
rokclmb3 years ago
Sorry if this has been said already but I didn't read through all the comments. This is a great idea that is very common in Japan. Many toilets have lids that have built in sinks. It is a great way to have a toilet and sink in a small room.
Our prison systems have toilet /sink combo units made from one piece stamped stainless steel, but they share the same drain ,the sink water does not help fill the toilet tank.as there is no tank to fill ,it uses a flush valve like your typical wall urinal.
Is this like the japan units?
Since it seems no one answered your question. In Japan the toilet/sink combo has been around since the 1960s and mainly found in public toilets. The water is used to rinse the hands and fill up the tank. Toilets without tanks are that way simply because they are in areas where the water comes in fast enough to create a flush. Most residential water supply lines don't allow water to enter a toilet fast enough to trigger the siphon effect, so the tank provides a solution. When a toilet is flushed, the water held in the tank cascades down with enough force to activate the siphon. Without that gallon or so of water pouring into the bowl all at once, the water would simply spill over into the siphon tube and remain more or less level without creating an actual flush.

I think they also set up prisons this way, with enough water power as to not need a tank, so prisoners can't hide things in the tanks.. or maybe make toilet tank wine.. haha!
Honda Enoch2 years ago
fill the pipe with sand. pack it down, fill again, keep doing this till you can not pack it any more. plug the ends and bend with ease.
EtCetera1123 years ago
Toilet water
EtCetera1123 years ago
Toilet water
My attempt at a retro fit cisten sink, mail order for UK fittings


95 % reclaimed materials, water saving, hygienic etc
First  I'd like to say that the idea here is one of the best, dare i say simply brilliant, ideas to innovate the toilet in years. That said, I think that the comments left in this posting prove full circle the errant views and attitudes so many of us have when it comes to anything "green".
 To all the plumbers that found problems with the design... dont  attack the poster for the flaws you find post solutions, if your licence is worth the paper it was printed on then you should have the knowledge to help himm fix the problem if not please seek employment at McDonalds.
 To the Americans who say "oh well water issues are a third world country problem" take another look at the globe buddy this is the same world the same planet and America is a new country when people have been here as long as they have been in Africa we'll have the same problems
 And the scientists the US goverment pay to be smart are too busy determining that santas reindeer were female and creating super computers thats only purpose is to test the theroys of Newton and Einstien.
 We need to get together and get it together, adress the problem and and make sure the money goes to the right places   
Im an american, i didnt see anyone here ( american or otherwise ) say that water was a third world problem. As for the critics, i think that instructables welcomes critcism when it helps to solve problems. Many of these instructables are " in the works " and are open to improvement, such is life in general.
To attack people as you have is of no help at all. Now ,go to your room til you can play well with the other children. ( of course that last part was a little brevity to lighten the mood ) Great ible-- i recently saw a toilet that used the water and the pressure of it comming into the tank to forse the water and waste down the sewer line--ingenious!!
Big thumbs up from me.
great idea! will do this at my home :)
I think this is super, you don't have to touch the faucet before and after washing like with a standard sink (the fatal flaw in no touch soap dispensers). Better yet, if the sink begins to run when you flush, there is no excuse not to wash. (I have a family member whose excuse is "I don't pee on my hands." As if that was all there was to that.)

I can't do this to my john now (I rent), but I will do this and some other grey water utilizing hacks as soon as I buy my own place. The main hack I had already planned was to divert waste water from the washing machine to an outdoor cistern for use in the garden. All that will take is to extend and reroute the the drain hose.
I am currently redirecting the waste water from my washing machine into the toilet, so we are no longer using any excess water to flush (water is precious in Israel). Let me tell you: the water that comes out of the washing machine is nasty. It junks up the inside of the tank and smells worse that the stuff we are flushing down.
Try filtering the water before using it to flush the toilet. That will help keep the pipes, tank, bowl and everything else clean. It will not smell.

Thanks, bennelson, that is a great setup that you have. It is impractical in our current apartment, but I will remember that for our next place! Could you mention on that page a bit more about the soap that you use. I saw mention of it being locally-made and eco-friendly in the comments, but more information would be great.

Thank you!
The idea behind this is that you can do it to any toilet without messing up the original hardware. You just have to find a place to store the tank cover, such as under the sink, till you are ready to move out. Then simply remove the made top, reattach the original rubber tube, and put the original cover back on. Then you can use it at your new place with a little tweaking. Also, grey water from a washing machine would contain any soaps/detergents you used to wash them with. Unless you are using some super organic stuff that is tested plant safe I would not water anything with it. Talk about a quick way to kill your landscaping. = )
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