Question on gray tanks

[kingdaddy]

On my trailer (3580 RL) there are two gray tank handles...one in the convenience center along with the black tank handle, and one tucked away near the tires on the frame.
My question is, every spec sheet I see says there is only 1 gray tank (93 gallons "total") which seems to make no sense if there are two valves. There is only one sewer outlet of course, and I assume some other models may be the same?
Can anyone clarify this for me? thanks!

[mhs4771]

Very simple: You have two approx 45 Gal each Gray tanks.

[Mikendebbie]

I am guessing…one gray tank handles your kitchen sink, and that handle is the one near the tires. The other gray tank handles your shower + bathroom sink…the handle in the convenience center is for that tank.

[rohrmann]

On our rig, the gray and black are next to each other, both the same 53 gallons, and the remaining volume is 40 gallons for the galley tank.

[Carl n Susan]

Originally Posted by kingdaddy

....My question is, every spec sheet I see says there is only 1 gray tank (93 gallons "total").....

I believe the brochures/spec sheets all say 93 gal of grey water. I have never seen where they wrote there were two tanks. Hence the #1 newbie question of the MOC has always been "why is my sink full of water when I have drained the tank?"

[kingdaddy]

Yep, I figured they just combined the total capacity of the two tanks...seems like I saw the capacity of the two separately at one time, but today everywhere I looked at the specs online it said just 1 gray tank which I was almost sure was not correct...

Thanks for the info!

[kingdaddy]

Originally Posted by Mikendebbie

I am guessing…one gray tank handles your kitchen sink, and that handle is the one near the tires. The other gray tank handles your shower + bathroom sink…the handle in the convenience center is for that tank.

Yeah, that is what I have always assumed. I think I probably actually read that at some point a few years ago...but then I was seeing everywhere I looked that there was only 1 gray tank which made no sense.

Just got home from dry camping for 8 days...we had been wondering which tank would be the first to either go dry (fresh tank) or fill up (gray water).

Since we had the two tanks for gray water, it was the 66 gallons of fresh water that we ran out of first. I was pretty sure (hopeful?) it wouldn't be the black tank...

Fortunately it was on day 7 and we had some extra water available for the last day...

[timandsusan]

Way back in 2006, as a Newbie, I learned about the Mystery 2nd Gray Tank. Came home after 1st trip and went to dealer because sink was full but I thought the gray tank was empty. The boat salesman who had never stayed in an RV did my PDI--skipped this because he was well ____________! So, yes there are 2 gray tanks and both have a separate handle.
By the way, this boat dealer was the only Montana dealer in San Antonio. And further it went out of the RV and BOAT business abut 2 years later! Don't miss them.

[TomHerod]

I know this is an old thread, but I was SAVED by a post on another thread regarding the kitchen sing having it’s own gray tank and a “mystery” location for its drain pull. See the attached photos for the one on our 2010 Montana.

[kingdaddy]

Thanks for posting the photos Tom...interesting that your handle hangs down like that!
Not sure how many of the Montana models have the second grey tank with the semi hidden valve handle? Just depends on how the kitchen sink is plumbed into the drain system I guess.
It's kind of nice, because we can use the kitchen sink more often than we might otherwise to avoid filling up the larger (bathroom/shower) tank before the trip is over.
We just did this again on a 6 day dry camping trip and we ran out of water again before either gray tank filled...which is what you would expect, unless you take long showers!

[twindman]

I am pretty sure my bathroom sink drains into the black tank. Looking behind the pass thru wall, I can see the pipe connect with the toilet drain, rather than the shower. Fortunately we don't use all that much water in the sink.

[kingdaddy]

Originally Posted by twindman

I am pretty sure my bathroom sink drains into the black tank. Looking behind the pass thru wall, I can see the pipe connect with the toilet drain, rather than the shower. Fortunately we don't use all that much water in the sink.

It would be nice to know how the drain systems work (i.e. how they are plumbed) on the different years and models of our rigs.
It would help know how to manage the filling of the various tanks while dry camping!
Where we were last week, there was no dump station at the campsite, the nearest one was miles away in town, and getting my rig in and out of the site I was in would not have been something I wanted to do just to dump the grey tank during our stay!