Someone here recently commented about replacing either the valve or just the seals and mentioned it being difficult to manage.
When I replaced our valve a few years ago my main problem was keeping the seals in place when reassembling. This link indicates you should coat them with a grease on both sides like Dow-Corning 111.
Sticky black water valve perplexes – RV Travel (http://rvtravel.com/sticky-black-water-valve-perplexes/)
Jim
You can also use vaseline, BUT - long term, any petroleum based product will degrade a neoprene rubber. For something like the seals, it would take some years. Mine are two years old since changing, using vaseline, and so far they are fine. If you have a dive shop nearby, you can get silicone O-ring lube. It works like vaseline but will not degrade the rubber.
Ken F in NM
You can also use vaseline, BUT - long term, any petroleum based product will degrade a neoprene rubber. For something like the seals, it would take some years. Mine are two years old since changing, using vaseline, and so far they are fine. If you have a dive shop nearby, you can get silicone O-ring lube. It works like vaseline but will not degrade the rubber.
In a pinch, dielectric grease will also work, having a silicone base.
Larry