RV plumbing is a BIG issue to most RVers. Many travel trailers and 5th wheels have two separate gray water dump valves. Usually one gray tank drains into an exit drain pipe shared with the black water tank, while the additional gray water drain is located elsewhere.
This type of arrangement makes it easier for the RV manufacturer but harder for the end user. If you own a rig like this you need to figure out how to link the two drain pipes externally.
RV stores sell “Y” adaptors for this purpose. You can also purchase connectors to assist you with this project.John Hass from Glen Arm, Maryland is an avid Rver.Here is a photo of his Coachmen travel trailer with two separate dump valves, one forward of the wheels and one aft.John opted to make his own “Y” connector using a standard stick house black pipe “Y” connected to an RV male coupler. He used flashing, caulking and hose clamps to fashion this homemade adaptor.Since the location of the sewer hole varies from park to park, John decided to make one end of his hose shorter. Whether the sewer dump hole is forward or aft of his tires he can simply swap the position of the hoses to accommodate the situation.Helping you stay connected – Jim Twamley, Professor of RVing