[Richard]

Of course you can recycle the water bank to the tank. But the rejected water from the RO system is higher in mineral content than the water fed to the drinking water tank. So now you are feeding high mineral water into the holdling tank. Of course you are diluting that water with fresh water each time you refill. So an algebraic expression could be crafted to calculate how high the mineral content of the tank water would rise if one knew how much water was used for other than drinking, the mineral content of the incoming water, and the ratio of drinking water to other water use.

I was just trying to make the point that the reject water has a higher mineral content, and you would be raising the mineral content of the water in the holding tank. Kind of counterproductive when what you are trying to do is reduce the mineral content of the water.