jerryc41 wrote:
Right, so where's the savings? Water is being taken from the central supply, and then it goes into the tank to be flushed away later. Instead of flushing 1.5 gallons, it will flush 1.6 gallons. It is a good idea to save space and avoid the need for a sink and all its plumbing, though.
No the tank would have no water to start. All the water it uses for flushing coming from the sink above. No washing hands no flushing.