Hack a Toilet for Free Water.




About: Instagram (@georglavoie)

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.

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Step 1: 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

Step 2: Locate the Parts and Trace

Remove the lid from the toilet tank. Locate the over flow tube, gently remove the rubber tube going into the top of it. Take the small plastic funnel and stick it in the tube. Now take a straight edge and span it across the walls of the tank next to the funnel, and mark the edge on the funnel. Now remove the funnel and lay a piece of paper of the tank and trace out the walls and the location of the over flow pipe in relation to them. Next take the lid from the tank and trace it onto the sheet wood.

Step 3: Cut Out the Lid

Cut out the shape of the lid with a jig saw from the wood and clean up as necessary with sand paper. Now take the paper tracing of the tank and cut on inside wall line with scissors. Now center the tracing on the new wood lid, and take the center punch and mark the center of over flow tube on the wood lid. Using this mark as center drill a 3 inch diameter hole with the hole saw.

Step 4: Making the Sink

With a marker extend the line on the funnel so that it goes all the way around, cut on the line with an Exacto knife. Now take the metal bowl and create drain holes in the center with a small drill bit, making sure the final drain is no bigger than the top of the freshly cut funnel. Next place the funnel on the bottom of the metal bowl and apply liberal amounts of caulking glue on the crack between the bowl and funnel.

Step 5: Faucet

The faucet is made from copper tubing bent into an upside down "J". To bend the tubing without kinking it, tightly wrap the wire around the section to be bent and carefully bend it with your hands, retightening the wire occasionally. Trim off the extra tubing with a tubing cutter. Drill a half inch hole with a spade bit, 3 inches away from the large hole in the wood lid. Force the long end of the copper "J" into the hole, friction should hold it in place.

Step 6: Bracket in Place

To keep the wood lid from sliding around on the tank you can attach brackets. To figure out where the brackets need to be, flip over the lid and center the paper tracing of the tank on it. The brackets should be against the outer edge and attach with small wood screws.

Step 7: Installation

Back inside the toilet tank locate the rubber tube that was inside the over flow tube and follow it back to the float valve, and pull it off. Now attach the 4 foot vinyl tubing. Push the other end of the vinyl tube through the bottom of the wood lid half inch hole and up though the copper tube until just before it sticks out the other end of the copper tube.
Now lower the new lid onto the tank making sure the vinyl tubing does not interfere with the internal mechanisms in the tank. Take the metal bowl with the funnel attached and make sure the glue is dry. Now look down the 3 inch hole in the lid and you should see the over flow tube. Take the bowl and funnel and lower it onto the hole, the funnel needs to go into the over flow tube.

Step 8: Finished

The sink is now complete.
I would recommend putting some kind of water proofing on the lid to protect the wood.
Check out the video of the sink in action.
Thanks for viewing my instructable.

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399 Discussions


1 year ago

You don't know what you are doing, most toilet cisterns use for the incoming water supply lead solder on the copper pipe, so it wouldn't be a good idea to use this for drinking or washing your hands.


3 years ago

actually its not free water !! because it come from main water of house!

1 reply

Reply 2 years ago

Yes it is free water.

you are reusing the water you already use so it is free.

or half price if you realy want to split hairs ;-)


2 years ago

There are two American-made toilet sinks out there ("Sink Twice" and "Sink Positive"). Sink Twice in its basic model fits toilets with tanks from 13 inches to 17 inches. With an expansion pack, Sink Twice fits toilet tanks up to 22 inches wide. Sink Positive is probably a better option for toilet tanks larger than 22 inches wide. Sink Twice is the most efficient on the market because it incorporates "fill cycle diversion" technology to make your toilet even more efficient. On top of that, you can wash your hands with the clean water and flush with soapy water. It is pretty cool and if it saves about 1 gallon per flush (more or less), with 5 trips to the bathroom per day and 4 people in your family using it, you are saving 20 gallons per day or over 6,000 gallons per year. Not too shabby! Sink Twice often pays for itself in months and it is available on Amazon.com.

I do hate to sound negative, but this 'hack' isn't that clever IMO.

Washing your hands in such an uncomfortable position is bad design: worse,

washing your hands on a toilet is poor hygiene design ( Treehugger has written a lot about the problems inherent in placing washing facilities in close proximity to a lavatory pan ). And having 'grey' water sitting stagnating is another area of concern.

I do share the author's desire to avoid waste and am planning some kind of system in my house. I'm in the UK where water shortages are considerably less severe than in the USA, but I still abhor waste, especially since the cost of cleaning water is considerable.

I'm also lucky in having a large roof area. When it rains the entire run-off is channelled into a big bucket and, as yet, I cant cope, but it isn't finished. The master plan is to collect it in one of those 1000L containers ( in the form of a cube: do you have them? ) This will be pumped into the cistern, with suitable controls. The water should be clean enough not to cause problems on standing.

As for 'grey' water: there will be another collection system whose contents are intended for the garden, so, if it gets a bit yucky, it wont matter too much.

Keep up the good work.

13 replies

@null, I agree with your concerns. I've never seen a cistern with a hose like that into the overflow, I think UK Regulations don't allow such things?

Regarding grey water: It's not a good idea to store grey water for long periods, the water gets stale and loses oxygen. Please have a look here for more details:



Hello Agulesin,

You dont say where you are from. I dont know if UK regs disallow this hack, but, as I say, I think the design is flawed and wouldnt use it myself. Having said that, at least the guy is trying. His design is not rubbish, but I think it could be improved.

My own plan wont get installed for some time because other things take priority. Nevertheless, the idea is there: divert the roof run-off into a HUGE container. It can be used ad libitum to fill a cistern. The power required to pump the water is not great, so you could use a solar panel + battery to insulate yourself from problems with the Grid. Remember, this is just one idea and maybe it could be tweaked. Suggestions always welcome, if accompanied by a 10UKP note.




Reply 3 years ago

UK Water Regulations prevent the contamination, wastage, and erroneous metering of water. This design has a decent air gap between the 'tap' and bowl, and, while the bowl outlet runs into a cistern that might be considered contaminated as it is part of a toilet, I really can't see a problem developing such as would affect the cold water supply. Obviously it's not type-approved stuff so technically it's illegal (same as fitting a hosepipe without a nozzle on the end is illegal), but I think prosecution would be extremely unlikely. The vinyl tubing could possibly contaminate the water if it's not drinking water grade, so it would be good to fit a (one-way) 'check valve' on the supply pipe feeding the float operated valve.

Building Control might not approve of the fact that the outlet from the bowl runs straight into the pan (could it block and allow the waters to mix?), but I don't think it's the sort of thing they care about that much really. The 'vanity' pipe is not common in the UK and probably wouldn't meet Water Regulations, but some are in use over here anyway.

Personally, I'd be happy to have this in my house, but would prefer the water to run into the cistern, not the overflow pipe. That said, my WC uses hardly any water to flush anyway and I prefer to wash my hands at a washbasin - but if I had an old 9l flush cistern, I'd be tempted to give this a go.


Reply 3 years ago

I've seen a cistern with a hose. It probably didn't comply with Water Regs. And it was broken, so I replaced it with a compliant valve.


Reply 3 years ago

I hope your pump will be hand operated, because otherwise the carbon emissions from using electricity to force the water up (or lack of contribution to the grid if you have a PV array) will outweigh the benefit from saving the water?


Right! I think this is a terrible idea.

Not wasting water would be solved better with reducing the water level you store in the tank and following these simple principles.

If it's yellow let it mellow.

If it's brown flush it down.

Plus, I don't know what a vegan hippy diet does for stool but what doesn't evaporate into rainbows and lollipops should flush with less water.



Reply 4 years ago

This type of toilet sink is standard in Japan, and they have no problems with it.

Makes the toilet easier to clean too. No downside. *^_^*


The greywater stagnation is only an issue in a restroom that gets very little use. Our house has 2 washrooms & 6 people living here, to say nothing of visitors. The longest our toilets go without a flush is maybe an hour, 3 hours at night.

Besides, if you are using a handsoap with essential oils of tea tree, lavender, orange oil--the tank is going to stay fairly clean, regularly.

If you leave on a trip, just pour a dollop of bleach into the tank before you go, and if necessary, a dab when you get back. It requires very few ppm (parts per million) to make an unsuitable environment for bacteria. Colloidal silver also works.And there are MANY food-grade enzymes available, as well. Plenty of options.

Besides, the toilet bowl is going to be cleaned as usual anyway; just seems like such a non-issue.

As for awkward placement--also depends on your bathroom layout. Our guest bathroom would be fine--plenty of space beside the toilet to stand comfortably; not an option in the master bath, though. So I am trying this in the guest bath. Finding a different set up for the other one.

But I'm tired of flushing perfectly good water down the toilet.


Reply 4 years ago on Introduction

Excellent point, null. A fundamental principle of greywater is you never store it. What this instructable will do is result in a slimy, foul-smelling toilet tank.

But the basic idea has merit. Ken Kern wrote a book in the 70's called "The Owner-Built Home" in which he described a toilet design that used greywater for flushing. It did not store the greywater, but instead ran it through a sluice that flushed away the solid waste. That would work.


Reply 4 years ago on Introduction

@ iamuke: thanks. I suggested rain water as a better alternative. Well, it is, but that, too, may have problems of its own ( gosh, this environmentalist stuff is tricky ) One way round this is to have a number of smaller containment vessels for the rain-water run-off. I don't reckon that would be so hard. Fill the cistern with the oldest batch first. Possibly have a system where the newer water gets pumped into the older containers as they empty. If the older water starts getting manky, ditch it on the garden. Brilliant, if I say so myself. That will be 25 guineas. Have I missed anything?


Reply 4 years ago

So you're the person who has my handle. Nice to run into a fellow Sianeee!


3 years ago

A better method would be to just disconnect the rubber tube and cap it off, and just use the sink to wash your hands. Many/most toilets don't really need the rubber refill tube so it is wasteful to have it spray all that water down the drain.

Note: some toilets might need it; to test this, disconnect the tube and then flush. if the water is high enough to stop gasses from coming through, then you're good, but if the water level is too low so that gasses can come through, you need the refill tube (but you can probably reduce the flow).

1 reply

Reply 3 years ago

what the heck, how did my comment get posted four times?! haha