Thanks Patrick,
In the sump area, where the BD lines come up, there is a drain line(6") that runs under the addition and daylights on the other side of the house. The filter room has a floor drain in it as well in the event of a failure. All the real dirty water from backwashes goes this direction. For WC's, there is a valve to direct the water to a 2K gal. storage tank that in turn is used to irrigate the property.
Here's a couple shots of the viewing room without the plastic.........