After having issues with opening the black tank cap and having debris coming out prior to opening valve, I decided to replace the valve unit. I ordered it off Amazon and replaced the valve. Not as easy as I thought. Really tight space with gaskets being displaced multiply times. Also just to note I was able to turn my black tank emission ( don't know if that is the term), unit back and forth before replacing valve. While I was replacing valve unit I had to turn the emission unit back and forth to access the four screws. I finally replaced valve unit and started to turn the emission opening to the front and it would not turn to the exterior for emptying. I had tightened the screws too tight. Now I am thinking maybe I just needed to tighten the four screws initially so not to have a little discharge after I opened the cap. I don't know. But just a thought going forward to any of you with the same problem. I have a 10 yrs old LD with low mileage. Not a full timer. Going forward, I can now do this without a second thought . Continue to learn more from mistakes than accomplishments :o