Bathroom sink draining into the black tank!

[2014Fuzion300]

I have been kind of suspicious because my black tank fills up very quickly ( but not 100% sure if something was not on the sensors). However last night the temperature was going to drop dramatically to the teens so I drained the black and I left a little water running in the bathroom sink so it would not freeze up!
Thank God I was still up watching TV when I heard like a pressure valve opening in the bathroom. I quickly went to it and saw air coming out of the toilet.
Black tank was full!!!
How is this possible? Is it normal for some campers? My old camper (Outback 23KRS) was different, and it took forever for the black water tank to fill up.
If it is not normal, how complicated is it to fix it? The camper is new so it is still under the warranty, if it is a warranty issue.
Thanks for your input!

[sbmarks3]

I've owned a lot of campers over the years and I have never heard of one that had grey water plumbed into the black tank. If your grey tank is open and draining properly with the kitchen sink, I would turn off the kitchen sink and turn on the bathroom sink to see if water drains. Does the 300 have one or two grey tanks?
I would call your dealer, could be a warranty issue.
Good luck

[Dreamsongs]

My sprinter 31fls has 2 sinks in the bathroom (why they waste room on 2 sinks in beyond me, but we love the extra counter space).

One sink drains into the gray tank, and yes, one drains into the black.

I found out the hard way. When sanitizing the water system, the sink on the left quit draining. I thought it had a clog.

I went to work the next day. Came back to find the sink empty, water on the floor by the toilet, and an awful smell!

Turns out that the toilet seal is not meant to hold pressure.

The water from flushing the sink faucet filled up the black tank, backed up the sink, then slowly drained out through the toilet flange seal.

Fun!

I called Keystone. They said yes it was meant to be that way because the black tank is harder to fill than the grey tank.

I think they were just trying to save money on a couple feet of pipe!

Good luck!

Dave



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[2014Fuzion300]

Is it possible that it was caused by an overflow valve? Because something got frozen in the gray tank?


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[Stublejumper]

Our 341 tg has 5 tanks ,fresh water of course,2 Gray and 2 black . The back bathroom toilet drains to rear back with the sink in that room ,the kitchen sink drains into rear Gray tank ,the front bath shower and sink goes to front Gray and toilet to front black. I to had to find out this the hard way as well. You would think a $60,000 trailer should come with a 5 cent piece of paper that says how it is plumbed. I know I have to supply this info my customers.

[2014Fuzion300]

Interesting,
I called Keystone today and after given them the VIN number the lady I spoke to said that she had the plumbing diagram in front of her. She said that the sink in the bathroom is not supposed to drain into the black water tank according to her diagram...
After I explained to her my problem I told her that I was going to take the camper to CW for a warranty repair. Then she talked to a production guy (?) and this guy said that it was possible to have the bathroom sink draining into the black water tank....
Bouncey!!!


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