Sink goes to back tank?

[Fredski007]

Only had dx3 for two months, now on second trip and found that the bathroom sink drains into the black tank. Sure does fill the black tank fast! What genius designed that system? Now when black tank is full the sink won't drain!
Does anybody else have this stupid setup or was somebody drunk during my build?

[rockfordroo]

It's not uncommon for a sink to drain to a black tank. It's dependent on floorplan:
location of tanks, sinks, showers, etc. If there's something in the way between a sink and a grey tank, like an axle, they'll go to the black tank instead.

Similar to having 2 grey tanks. Sometimes the drains of both greys will come together with the black; sometimes one grey has it's own drain because something like an axle is in the way, so you either need to move your drain hose between them or use a wye in your drain hose(s).

[Fredski007]

Thanks for the rapid reply, sounds logical. P poor design for dry camping, guess we wash more in front sink.