Dump valves do not hook directly to the 3" ABS fitting, from the outlet run PVC or ABS piping to the outside of the trailer, a dump valve is added to the piping.
The 1.5" Gate Dump Valves are usually used to connect piping not for dumping because a sewer hose does not connect to this valve.
For more information please be sure to view our WATER TANKS HELP PAGE and go down to the Waste Water Tanks & Help.