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  1. #1
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    2022 Momentum 349M Gray Tank(s)

    New owner of a 2022 349M with the half-bath option. My gray tank capacity is 104 gallons, and the monitor panel shows 2 gray tanks. I can only find 1 gray tank valve. I’ve read various threads here suggesting that either the tanks are connected and drain through the single valve or that there is another valve near the axles. Neither of those seems to be the case. My issue is that one tank shows full after just a couple of days of dry camping (and no long showers), and the other tank shows empty. I tried the Valterra valve trick (closed gate valve at the discharge connection and opened gray tank valve), but the tanks don’t equalize. Am I missing a valve?

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    Quote Originally Posted by Hookem59 View Post
    New owner of a 2022 349M with the half-bath option. My gray tank capacity is 104 gallons, and the monitor panel shows 2 gray tanks. I can only find 1 gray tank valve. I’ve read various threads here suggesting that either the tanks are connected and drain through the single valve or that there is another valve near the axles. Neither of those seems to be the case. My issue is that one tank shows full after just a couple of days of dry camping (and no long showers), and the other tank shows empty. I tried the Valterra valve trick (closed gate valve at the discharge connection and opened gray tank valve), but the tanks don’t equalize. Am I missing a valve?
    I would think you have another handle some where. Do you have a separate dump port or single?

    Full-time Traveling Family ,'21 Momentum 395MS-R, '21 F450 King, 2000watts solar, Dual Victron MP-II 12/3000 2 x 120v, 1220ah LiFePo4

  3. #3
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    I have a second dump port under the garage, with a single handle/valve. I was told that was for the rear black tank.

  4. #4
    Rolling Along jjbbrewer's Avatar
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    Quote Originally Posted by Hookem59 View Post
    New owner of a 2022 349M with the half-bath option.
    I have a 2021 349M with the 1/2 bath as well.
    Quote Originally Posted by Hookem59 View Post
    My gray tank capacity is 104 gallons, and the monitor panel shows 2 gray tanks.
    I'm pretty sure you have one grey tank. The shower and main bathroom sink drain into it. My panel shows a 2nd non-existent grey tank, too.
    Quote Originally Posted by Hookem59 View Post
    My issue is that one tank shows full after just a couple of days of dry camping (and no long showers), and the other tank shows empty.
    Based on my measurement (using a water flow meter) of the rear black tank, it could be that the grey tank gauge is a "scare gauge" - meaning that it registers much more full than it really is.

    For example the rear tank indicator goes from
    • empty to 1/3 at 4 gallons
    • 1/3 to 2/3 at 8 gallons
    • 2/3 to full at 26 gallons
    • full to visible down the toilet at 45 gallons

    I haven't measured the main black tank nor the grey tank yet, but I will.
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    @jjbbrewer, thanks for a terrific post! Very helpful! I dumped all the main tanks yesterday, so now I can watch the progress more closely. Based on what’s you’ve observed, does that mean the kitchen and rear bathroom sinks drain into Black 2? I ask because the rear bathroom hasn’t gotten much use, but Black 2 does show 1/3 full. Is the main Grey tank a single 104 gal tank, or 2 52 gal tanks? I should probably ask GD that question. Anyway, thanks again!

  6. #6
    Rolling Along jjbbrewer's Avatar
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    Quote Originally Posted by Hookem59 View Post
    @jjbbrewerBased on what’s you’ve observed, does that mean the kitchen and rear bathroom sinks drain into Black 2?
    Yes, exactly.
    Quote Originally Posted by Hookem59 View Post
    Is the main Grey tank a single 104 gal tank, or 2 52 gal tanks? I should probably ask GD that question.
    I really don't know. If you do ask them, please let me know since we probably have identical setups.
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    Any further confirmation on this post? I also have the 2022 349M and have never used the rear bathroom. My Grey 2 tank doesn't register any use but by using the kitchen faucet only my black 2 does register as showing use. I do believe the kitchen and rear bathroom sinks drain into Black 2. I would like confirmation if anyone has confirmed.

  8. #8
    Left The Driveway
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    I have a 2021 349M without the 1/2 bath option.

    I have two gray tanks. The kitchen sink drains into the 2nd gray tank and the pull valve for this is behind the rear axle in garage area.

    Good chance your bathroom and kitchen sink both drain into a single tank which makes that 2nd gray tank a black tank if the bathroom get used.

  9. #9
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    Thank you @BarrySmith, my back tank is black tank and has a black tank dump valve behind rear axle. It sounds like my suspicion is correct that it's the same tank. I just don't like the idea of that tank possibly filling up and backing up to kitchen sink with sewage...

  10. #10
    Rolling Along jjbbrewer's Avatar
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    Quote Originally Posted by jbox5000 View Post
    my back tank is black tank and has a black tank dump valve behind rear axle.
    Same with mine.
    Quote Originally Posted by jbox5000 View Post
    I just don't like the idea of that tank possibly filling up and backing up to kitchen sink with sewage...
    IMHO, you'd have to really try to do that.

    The kitchen sink (and the bathroom sink too, I think) have traps that are higher than the toilet flush valve, so you'd be seeing some "issues" in the rear toilet before anything came up in the kitchen. I filled my rear black tank to the top (described here) and the sinks were fine.
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