Our Blue Ridge (made by Cardinal) has a single "blue" tube extending from beneath the underside cover near the rear of the unit. It had a plug in it so I removed it and screwed a elbow into the female coupling and extended a pipe to the rear bumper with a valve on it.
Now I don't have to get under the thing any more to drain the fresh water tank (we do a lot of "dry camping" so we have to take the water with us).
Doug and Becky Ridgeway
2014 Blue Ridge 3600RS
2014 Ford F-350 CC 4X4 DRW 6.7 PSD