Momentum 385TH Half bath gray tank?

[Lightning]

This isn't a "How To" question, more of a configuration question. We all know the saying about "assuming" something. Our issue with "assuming" started the first time we drained our black and gray tanks. 385TH has two black and two gray tanks due to having a bath and a half. We "assumed" the gray 2 would flush the black 2 line. Not! So then we knew we needed to do an extra good flush on the black 2 tank before removing our drain line. Our next "assumption" was that the half bath sink would drain into the gray 2 tank along with the kitchen sink. Not! This realization arose after two unfortunate incidents. With below freezing weather, we leave the half bath faucet dripping to avoid the freezing of the water supply line (at source before the heated water hose we use). The first time we found water leaking under the sink, weren't sure where it was from, the sink was full above the trap, but the gray 2 tank wasn't full. Upon using the toilet in the half bath, it was suddenly full and "blew up". Talk about being DISCOMBOBULATED! So we cleaned the mess, drained the tanks, but remained confused. Until it happened again after extended freezing temps and leaving the faucet dripping. We keep an eye on the levels, but who would guess that...wait...are you ready...the half bath sink drains into the black 2 tank. Oh, and the water under the sink was the flush line vacuum breaker leaking since the tank level was over-full. Are we wrong to be surprised that sink water is going into a black tank? No one tells you how these are configured when you purchase the units. I had asked unrelated configuration questions from a service manager during our warranty period and he pretty much told me that he couldn't tell me what the layout was as they make changes all the time and one unit may be different from another. Really? They don't use construction plans and schematics during production? I've worked in manufacturing and this sounds strange. Why aren't we supplied with diagrams of construction/wiring, etc. when we purchase a unit?

So now I've vented and learned my lesson for sure about "assuming". If our toilet blows up again, it won't be for this reason.

[JCR GD]

GD may chime in but you are correct in your latest assumption. Rear sink goes into black tank 2. Probably cuz that sink normally doesn't have a lot of volume.

[Lightning]

Amount of volume aside, it would've been nice to know that. Gray going into a black tank...who knew? Obviously not me. The times this happened, we weren't using that toilet, so it was a real surprise when it got full.

[FT4NOW]

Ours is the same setup. It makes sense if you think about tank location in relation to the sources. The grey 2 is for the kitchen sink, it would be more difficult to plumb the half bath sink to also drain to that location. There is already a tank near the half bath, yes it's black, but much easier to plumb to that tank. Our washer also goes to the rear black tank, so it's mostly soapy water and doesn't need as much of a flush. When it's not winter I keep a hose connected to the tank sprayer line with a y adapter at the water spiget to make it easier to flush on a regular basis.

Sent from my SM-G950U using Tapatalk

[Lightning]

I appreciate y'alls comments, but my point seems to be lost. It's about information. This is our first RV, but regardless, there was no information about this.

[GDRV_Tara]

Lightning - Due to the build drawings being proprietary information, they are not provided with the owner's packet information.
Gray #1 and Black #1 are for the fill bath, Gray #2 is for the kitchen and Black #2 is the rear half bath.
If you have any other questions, please contact us at [email protected]

[Lightning]

Again, I appreciate these responses, but why aren't we informed with purchase or in the owner manuals, prior to an unfortunate incident. I guess I'm the only one to have this happen.

[MarkRizRV]

I agree with what you are saying, even in our small 2150 we are left to assume what gray 1 and 2 are connected to, we had to figure out. They could at least add that detail to the manual without sharing drawings or secrets

[Big Mike]

When I purchased my 385, my selling dealership informed me of the configuration of the tanks during my PDI, including the rear bath black/grey tank. I do agree though, the owner’s manuals could be a little more model specific and contain information such as this.

Big Mike