351M dump valves

[roadrunner2]

I Have a 2020 351M. Am curious to hear from other 2020 351M owners regarding how many gray tank dump valves you have? I have just one located at the nautilus panel. What prompts my question is a recent discussion with GD customer service about tank capacities and a DWV plan schematic (351M dated 4-17-17) sent to me from GD that shows a second gray tank dump valve specific for the kitchen sink. GD insists I should have two valves and suggests I take to dealer to rip apart under belly and investigate. I've used my rig enough to know kitchen sink, shower, and master bath sink all drain through the one gray dump valve I have. While my one control panel level monitor has a gray 1 and gray 2, only the gray 1 ever registers and is definitely driven by all three (kitchen sink, shower, master sink) sources. I'm thinking kitchen sink drain may be plumbed directly to the gray tank for the master bath or gray tank for kitchen sink is plumbed into master bath gray tank. I've said to myself on several trips that the gray tank sure does fill up fast. I'm going to measure my gray capacity and see if I have 75 gallons or 37 gallons.

[FT4NOW]

I find it hard to believe the bathroom sink, shower and kitchen sink are supposed to goto one tank. I don't have a 351, but my bathroom and kitchen sink layout is similar to a 351. I have 1 black handle and 2 gray handles in the Nautilus panel area. Physically my 2 gray tanks are stacked on top of each other and I could see how they could easily make that plumbing mistake during the build, but where is the second handle?

I would def pull part of the coroplast down to investigate, especially if you are missing half your gray water capacity.

Sent from my SM-G950U using Tapatalk

[offtohavasu]

There are 2 handles, 1 black and 1 gray tank at the Nautilus panel. That gray covers shower, bathroom sink, and kitchen sink.

Behind the rear wheel on the street side, there's a black handle. This handle is for the rear black tank which handles the rear toilet, sink, and washer.

[Rich38]

My 2018 351M is plumbed the same as offtohavasu.

1 - gray handle
1 - black handle
in front

1 - black handle behind rear axle on driver side.

[tamrick]

2019 here. front/1 gry 1 blk, rear/1blk.

[roadrunner2]

Thanks to all for the responses. Turns out as stated in other posts, I have 3 - 52 gallon waste tanks. One is dedicated gray for shower, MB sink, and kitchen sink. Must have got a greenhorn GD CS rep that fed me several pieces of bad info. and got me all worked up and on a goose chase. He actually sent me a schematic that said 351M and showed 4 waste tanks. So in the end I'm not missing a gray valve. Moral of story.... Don't believe everything your told..... even from the supposed authority.

[AppleOaksNY]

I am glad to know that I'm not the only one who has had the thought " man, this grey tank is filling up fast."

[FirstAscent]

I have a new 381M which is fairly similar to the 351.

Are you guys saying that you have just one gray tank that is 78 gallons?

I don’t have too much use in mine yet but it seems the front kitchen, shower, and bathroom sink fill up the gray tank, quite fast if it’s 78 gallons.

I have my parents and little brother in it now (due to all the fires in Oregon) and they filled up the gray tank in less than 3 days. Really made me think its 39 gallons in that tank.

Similar to you guys, I have 1-black and 1-grey dump valve in nautilus panel, and 1-black dump valve near rear axle.

I haven’t used the rear toilet or sink yet though.

But looking at this schematic GD sent me, it looks like there should be two black tanks and one Grey tank. Which means that each black tank should be 39 gallons each and the gray tank should be 78 gallons.

I’m assuming the HT (holding tanks) with sprayer is the black tanks, and the standard HT is the grey tank.

[DarylB]

I have a new 381M which is fairly similar to the 351.

Are you guys saying that you have just one gray tank that is 78 gallons?

I don’t have too much use in mine yet but it seems the front kitchen, shower, and bathroom sink fill up the gray tank, quite fast if it’s 78 gallons.

I have my parents and little brother in it now (due to all the fires in Oregon) and they filled up the gray tank in less than 3 days. Really made me think its 39 gallons in that tank.

Similar to you guys, I have 1-black and 1-grey dump valve in nautilus panel, and 1-black dump valve near rear axle.

I haven’t used the rear toilet or sink yet though.

But looking at this schematic GD sent me, it looks like there should be two black tanks and one Grey tank. Which means that each black tank should be 39 gallons each and the gray tank should be 78 gallons.

I’m assuming the HT (holding tanks) with sprayer is the black tanks, and the standard HT is the grey tank.

The (3) waste tanks are all 52 gal each.
There is only 1 gray tank (52 gal), the kitchen sink, shower & main bath sink all go into it.
The main bath toilet goes into black tank #1 (52 gal)
The rear half bath, toilet and sink as well as the WD drain all go into the rear "Black" tank #2

Grand Design comes up with the 78 gal gray & 78 gal black numbers on the specs by dividing the rear black/gray 52 gal tank in half (26 gal of each) and adding that to the front gray/black capacities, 52 + 26 = 78

[FirstAscent]

The (3) waste tanks are all 52 gal each.
There is only 1 gray tank (52 gal), the kitchen sink, shower & main bath sink all go into it.
The main bath toilet goes into black tank #1 (52 gal)
The rear half bath, toilet and sink as well as the WD drain all go into the rear "Black" tank #2

Grand Design comes up with the 78 gal gray & 78 gal black numbers on the specs by dividing the rear black/gray 52 gal tank in half (26 gal of each) and adding that to the front gray/black capacities, 52 + 26 = 78

Thank you! That makes sense after you explained it! Also will help me when managing waste water of sorts.