We have a new-to-us 2005 Wildcat. It is our third trailer, but the first with three tanks (grey, black, and galley). I find the valve configuration a little odd - perhaps I am just missing something. Would not be the first time...
The gray and black valves are to the front of the outlet, the galley is to the rear. All three use the one outlet. [ a picture would be great right here]
You can't empty the grey tank without also opening the black tank valve. That seems odd to me. We typically camp at partial hook-up sites, so it is not a big deal to dump black/grey/galley when we leave. Seems to backwash into and help clean the black tank.
At a full hookup site, how would I let the black tank fill up while draining the grey tank? Does anyone else have this configuration of dump valves?