Eco Bath is designed to recycle the water, which is natually rolling down from a washbowl. However, what if people use toliet more often than washbowl? Maybe, there would be an innocent victim who creates an illusion that the toliet bowl is out of order.
To prevent such sad situation, I think a dual water-tank which is composed of two parts; The left part contains recycled water and the right part contains tap water.
Outwardly, it looks a normal water-tank except two levers and a single LED. So, when the left part is full of recycled water, the LED becomes green light, then we can pull the lever for recycled water to flush the toilet.
Inversely, the LED stays on red light, indicating not full it yet, then we can pull the lever for tap water to flush the toilet.