There should be no problems with water quality. Although the water discharged from the water purifier is considered waste water compared to pure water for drinking water, in fact, this water has also undergone three-stage filtration, but it does not have did not pass through the final reverse osmosis membrane and was eliminated. Water from solar energy is used as domestic water and will not be consumed directly, so it is completely acceptable.
But there is a problem. The waste water coming out of the water purifier has no pressure. If you want to add solar power, do you need to add a pump to pump them?