QUOTE(Denali @ Mar 25 2014, 10:59 AM)
When you say "backflush", do you mean the tank flush or does your rig have some way of flushing back up the outlet of the tank?
Ours has a tank flushing connection that sprays water into the black tank at the top of the tank. We have never had a problem with ours, but I have seen several reports over the years of folks whose black tank flush has clogged up. Apparently, the sprayer inside the top of the tank has little holes in it to create a spray, and those holes can get clogged up. The fix is to remove the sprayer from the top of the tank and clean out those holes. Then simply reattach the sprayer to the tank and seal it with silicone.
Although I have never removed ours, the sprayer is pretty accessible on our black tank.
There is a check valve in the flush line to keep an overfilled black tank from spewing out that connection. I suppose that valve could be stuck on yours.
Thanks Dave, any idea how to access the sprayer? Also I can see the flush line valve under the sink, but how do I "unstick" that?
Suggestions would be appreciated.