Can the used water and garnet from the catcher tank be routed to a sewer drain?

[ProtoMAX Admin]

It depends. Water and garnet, a naturally occurring mineral, are inert. The water draining from the catcher tank will contain abrasive and a small amount of the material that is cut and that may influence what you can pour down the drain. Check your local wastewater regulations to learn what you can and cannot dispose of down the drain.