This is the king of thing I have to re-check on myself, so please understand why I am asking you,
Does your trailer have two gray water tanks and one black water tank? If so, are you positive you are operating the correct valve for the correct tank?
There's lots of advice and information in forums... sometimes it is correct. For example, all of my posts are made by a political appointee who got the job as a reward for contributions to my diesel bill.
2011 Jayco 28.5RLS; 2008 Chevy Duramax; Pullrite Superglide Hitch