Laredo 291TG/303TG

[SLIMSHADIE]

I have a 2010 291TG, that we bought last August. We love the camper. Anyways after a 4 day trip, I have never filled my black tank completely full.
I do use the black tank rinse religiously if we have hookups. I was close to full so I decided to fill the black tank full to the rim and flush due to some smells last time but did not have hookups. Any ways my outside kitchen sink would not drain so I dumped the grey tank. Still nothing. Dumped the black tank and it drained, so my questions is "Is my outside sink plumbed into the black tank?" I had a similar experience last fall, but didn't think anything about it. It didn't backfill, but would not drain after filling the black tank on purpose. The water wasn't dirty as far as just washing my hands, so there may be a check valve?
I will call Keystone in the morning to find out for sure! At first thought it was kind of gross so I bleached the trap and the sink for a while. My next thought is I'm always dumping the grey tank twice as much, so if it is the case, that will help and also help dilute the black tank since I'm always using the outside sink for stuff. :confused::confused:

[Seann]

It is getting more and more common to have one sink drain into your black tank so that you will have enough fluids for a full dump.

[SLIMSHADIE]

After calling Keystone, and did not get a straight answer,
"It may be plumbed into the black tank, which ever is closer and/or codes."
They wouln't tell me for sure, common sense it is.
So I was asked, concerned, Will it backflow into the sink?
"You should be careful, not to overflow the black tank, but there should be a vacuum seal to prevent it."
Well at least I know now and having 1 sink to the black tank is not a bad idea to disperse some of the liquids.