The Dandy Pro is a drill attachment. Simply insert the Dandy Pro into the chuck and spin the brush or roller into an old cardboard box (put the box into a bin liner to stop any leakage), allow the paint, water and solvents to dry on the cardboard and then dispose of it along with the normal household rubbish.
Paint should not be washed down the sink or taken to a landfill because the chemicals can leech into the ground or cause contamination that is dangerous to human and environmental health. Lowes suggests a few methods for paint disposal. For water-based paints: pour it into a container filled with an absorbent material like cat litter, sand, or sawdust and let it dry completely before putting it with your regular trash. For oil-based paints: dispose of as hazardous waste (contact your local hazardous resource center for instructions).
You’re right, the paint could clog your drain as well as pollute the water supply. I can’t offer any alternative solutions, but I would suggest that to avoid wasting extra water, soak the brushes and rollers first. And if you you are taking a break, instead of washing the brush, just wrap it in a plastic bag to keep it from drying out. Here are some ideas about what to do with any left-over paint you may have: http://www.squidoo.com/disposing-of-paint
It is wrong to wash paint down the sink. Paint is a safety hazard and is very difficult for landfills to dispose of. It is preferred that the consumer take responsibility of disposing of it.
If you use the Dandy you will not have to put anything down the drain!