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Water-saving toilet hack Answered

Toilets use fresh water, and lots of it.  Sure, you can buy a low-flow model, but you're still flushing with a (smaller) quantity of fresh, otherwise drinkable water.

Gregorylavoie decided to get double use out of that water by hacking his toilet.  It's a neat, reversible modification: after you flush, you use the clean, incoming tank refill water for handwashing.  Your slightly soapy hand-wash runoff fills the tank, and is saved for the next flush. 

It's a simple, ingenious way to save water with little to no effort.

What do you think?  Would you try this mod on your toilet?

This post has been sponsored by Pepsi. The Pepsi Refresh Project celebrates the people, businesses, and non-profits with ideas that will have a positive effect on our world.


elements chemically speaking has to be one molecule.

however water has been referenced in literature/art/ history as an elements (eg earth/wind/fire/water).

washing you hands while standing over a toilet can't be too clean. the soap will have an abnormal amount of bacteria on the toilet. Better to probably have a liquid soap or attempt to have the hand washing a little bit away from the toilet (although that logistically speaking is much more work, time and money).


6 years ago

this other one says water is not an element it is comprised of two elements, hydrogen and oxygen,


6 years ago



6 years ago



6 years ago

i put in the search line after i put is water a chemical, it said it is then i put is water an element and it said it is but it is also a chemical, everything is a chemical even air, chemists have told me how they can make water from oxygen and hydrogen and they can make all sorts of things using chemistry,


6 years ago

http://en.wikipedia.org/wiki/Water someone said water is not a chemical it is an element, but on wikipedia it says water is a chemical.

Lets pee on the sidewalk and save a BUNCH of water.

Nah, use the sink and clean a plate at the same time.


Thank you for all the input here and before i start my own version with Trespa and copper was wondering if others had attempted this and any improvements made please ?

Thank you all for the input here, just working on the same project using reclaimed Trespa and copper and would like to know if there are any other makers, or further improvements made that i could utilise ?

If anybody is still interested. There is an australian company called caroma. I think they also invented the dual flush toilet and they also have a toilet that does exactly what you have done.

 you sure know your stuff about toilets must spend alot of time on it!

I wouldn't do this, mainly because the soap would dry out the gaskets and plunger prematurely (which is why I also do not put the "blue things" inside the back of my toilet.  I would rather work it the other way around, but that is definitely more annoying. If you could use the water, in conjunction with the next "flush" without it having to set around the rubber plunger, or the gaskets of the tank, then I would consider this. 
Manually dumping a basin or bucket comes to mine as about the most annoying thing one can do in this respect.

 I kinda half agree here, I could understand maybe the gaskets of the tank, but what about the gasket of the toilet itself do you mean that too? I pour all kinds of crazy sh(t down my toilet all the time, does that mean the gasket is gonna get all messed up?

For example, regularly 3-4 pounds of dog fur and associated gravel water.

Oh no,  but some chemicals will dry out the gaskets and then they become brittle.   Soaps, detergents, chlorine bleaches, etc.

*the voice of experience.....*   LOL 

 Oh really? So even those "blue" toilet cleaners are probably harmful to the wax gasket?

wax?   I know they dry out, i.e. dryrot the plunger seal (the one on the flap)  and allow them to leak water into the bowl and have the tank constantly refilling itself.....and there are other "rubber" gasgets I have seen in some of the componants in some tanks....

 Nono, I meant the wax gasket used to seal the toilet to the floor/drain

Oh, I don't know about that.    I do know they warn against dumping chlorine bleach down the loo, but I am not sure if THAT is the reason or if it is because one might "burn their buns" if they splashed themselves :-) 

Actually the toilet gasket is made up of a solid piece of wax. It stays water tight unless the bolts in the back of the toilet come loose, then you have to replace the bugger

 Oh okay, yeah I've watched a few installed in my lifetime. I remember my dumba$$ lanlord putting a new one in our upstairs toilet. What does he do? He sticks the bugger on our burning hot woodstove to melt the one end before he put it in, also producing a large amount of smoke in the process. Needless to say my mother wasn't impressed.

Will soap (or my preference, non-soap detergent) dry out rubber gaskets even when they're immersed in water?  I know that the stupid bleach blocks damage the gaskets by chemical degradation.

It isn't "technically" a drying out (just like "dry skin" is technically skin deprived of natural oils and not just water, so soap and water do dry them both out).
  Really though, my biggest concern it that rubber "plunger" which takes so little warping to start to leak that it goes "on it's own", much less with assistance.
I haven't actually done any research into it, but I have seen rubberized products, um, hardened by detergents, or at least it appeared to be that way.
That is, it seems to shorten it's use. But I didn't "time it" to be absolutely sure.
I do know that excess water "dries out" leather products also (removes the oils from them),  both natural and synthetics.

There are weather/detergent proof rubber gaskets out there; they use them in washing machines; but, I don't think that there is any expectation of detergents in the back of a toilet bowl, so they may not use them there.  If they do, I am all wet, and I apologize for even mentioning it.....

I know that overuse of detergents (or having any residue left behind) IS a concern for mold, mildews and bacteria....


Thanks, Goodhart!  I appreciate the explanation and detail.  You're quite right about the action of both detergents and water on thngs like skin, leather, and presumably non-vulcanized rubber!  I hadn't made that connection.

So essentially what is being installed is a grey-water holding tank that does not fully get rinsed out everytime it is flushed(the flapper mechanism is an inch or two above the bottom of the tank) thus defeating the purpose of removal of waste - with the possible migration path including the germs or bacteria washed from the hands which leads to the bidet discussion or the shower attachment to toilet discussion.

Still wouldn't be drinking from it.

After a bit, I would bet it would smell badly too (inside the toilet tank)

Cesspool inhouse. Reverse engineering at its best.

Hmmm, a terrorist's dream machine?  Grow your own diseases ! J/K

Hang on, I have to go shock the toilet with chlorine and check the pH before I use it.

  But, but that'll ruin the gaskets and the plunger

Check out some of the commercial versions referenced below - sounds like they've either solved most of these problems, or (like most toilets) figure you'll be replacing the gaskets, flapper, etc at some rate anyway.

Hmm,  true, in the city, one must do so regularly anyways since the chlorine in the water plays havoc on them.

In the countryside, where I grew up, we had a  ritual at the 1/2 year mark,  where we shut off the input valves,  flushed as much out of the top as we could, and then unbolted it and took it outside for a good rinsing....sand, silt, and a lot of other stuff ended up in there....as I recall. 

I guess it was better then trying to get to the trap every six months :-) 

Sand and silt?  Were you running on well water?

Yes,  but we normally only got the sand after a heavy rain storm though :-) 

I guess one way or another, nothing is maintenance free :-)

(correct spelling in this copy)
You are quite welcome.   On further thought though, and after some discussion (below) with canida, maintenance is probably not THAT much effected, so I am probably being paranoid again. . . 
Yes, and as I assume caitlinsdad is saying, the bacterial content would probably increase inside the tank exponentially.

8 years ago

 What about adding a valve to the sink portion of the system(like a regular sink), and automating the tank to fill after a few minutes. That should solve the courtesy flush issues. You also won't be on a limited hand washing schedule. Though the refill cycle would probably allow you plenty of time to wash thoroughly.  You could also have it tweet every time you flush if it's automated...

Deek D

8 years ago

Now only if they could find a way to use the post-flush water in a shower......

No, what a great idea.....love the concept....




So, you wash your hands with cold water? Not very effective, or comfortable for that matter. Do you fill your toilet tank with heated water?
Not only that but that piece of OSB on the top of the tank looks great in the bathroom too.....

OK, I'll say what lots of you wanted to but didn't...
This is one of the dumbest "green" ideas I've ever seen...

cold water is just as effective as warm water for hand washing as long as you use soap. rarely does tapwater get heated to a temp that kills all bacteria...and even if it did, rarely would someone wait that long for the temp to get up to scalding. As far as "comfortable",  I imagine this isn't even a thought if you live anywhere 45°N Latitude or below...

Just my thoughts. =)

Yes, washing in boiling hot water is uncomfortable to say the least ;-)

Not terribly eco-friendly to let the sink run while you wait for your water to warm up enough to comfortably wash your hands. Where I live we have reservoir water, and when the reservoir runs low from people wasting water the entire city goes on drought alert and the cost of water skyrockets. 

So 2-5 mins of fresh drinkable running water down the drain while you wait multiplied by billions of people who have running water, multiple times a day is actually quite a huge waste.

Also germs and bacteria tend to breed in warm moist areas... So hopefully you dry your hands well.