Valterra's T38 fixed wye double valve assembly with 3" hub x 1-1/2" rotating hub x 3" bayonet end with cap will allow you to plumb your RV black tank and your RV grey tank into one outlet allowing you to use one dump hose to empty both tanks. Makes dumping tanks easier and cleaner, just dump the black tank first and then the grey tank to wash any black tank residue out of your RV sewer hose. Please note: Paddle is slightly smaller than opening to ease opening/closing. Valve seal gaskets block any gaps to ensure no leaks.