Shut off the toilet and sink from the water supply line located underneath and attached to the wall. Next replace the tiny fill tube leading to the overflow pipe located in the tank of the toilet with a vinyl tubing. This vinyl tubing is to be connected under the sink where the hot water line would normally be connected. Some clamps may be necessary to ensure the tubing is watertight. Once this is accomplished, part of the toilets fresh water should now flow through the sink when the toilet is flushed, meanwhile, the main fill valve fills the toilet tank as any toilet would. Finally, to reuse the water dispersed from the sink's faucet, a series of PVC pipes are arranged with a sufficient drop to allow the water to flow back towards the toilet tank and into the overflow tube as originally designed and end up in the toilet bowl.