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.