Fresh water tank will not fill on 2021 Tab 400

ESH
ESH Member Posts: 27
in Heating/Plumbing & Winterizing
Hey gang,
We have the P3 Nautilus system and for some reason we cannot fill the fresh water tank.  I tried the PowerFill setting, and also tried to siphon water into the tank using Sanitize setting.  Water just gushes out of the tank overflow drain.  I can get water to go directly to the fixtures, but not the tank...  At wits end.  Any assistance is super appreciated!
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  • ChrisFix
    ChrisFix Member Posts: 743
    @ESH
    Are you certain that you have the drain valve to the fresh water tank shut?
    The location is very near the overfill relief drain, so the water comes out around the same location.
    With the fresh water tank valve open, water will immediately come out when you attempt to fill the fresh tank.
    2025 T@B 400 Boondock Black Canyon with 400Ah Battle Born and Victron Multiplus 3000
    2025 Honda Ridgeline Black Edition with Redarc Trailer Brake Controller
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  • ESH
    ESH Member Posts: 27
    @ChrisFix
    Apologies for not responding sooner.  Yes, I am certain.  It is coming out of the blue drain pipe below and to the front of the access panel of our 2021 Tab 400.

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  • ChrisFix
    ChrisFix Member Posts: 743
    edited August 2021
    @ESH
    That is the low point drain for the cold water...which needs to be closed as well.
    Look inside the Nautilus access panel, you'll see two small silver valve handles - one for the cold water (blue pipe) one for the hot water (red pipe). They both need to be closed - which is rotated 90 degrees relative to the pipe.

    2025 T@B 400 Boondock Black Canyon with 400Ah Battle Born and Victron Multiplus 3000
    2025 Honda Ridgeline Black Edition with Redarc Trailer Brake Controller
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  • manyman297
    manyman297 Member Posts: 1,433
    The blue pipe is the overflow drain for the fresh water tank. Are you going off of the digital gauges inside to see if your fresh water tank is full? I wonder if it’s reading as empty but the tank is full. You can reach under the trailer in between the cutouts in the frame and knock on the fresh water tank to see if it feels full. That overflow drain is just a piped into the top of the tank so the only way water is coming out of there is if the tank is full. 
    2021 400 BD
    2020 Tacoma TRD Off-Road 
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  • ChrisFix
    ChrisFix Member Posts: 743
    edited August 2021
    manyman297 said:
    The blue pipe is the overflow drain for the fresh water tank. Are you going off of the digital gauges inside to see if your fresh water tank is full? I wonder if it’s reading as empty but the tank is full. You can reach under the trailer in between the cutouts in the frame and knock on the fresh water tank to see if it feels full. That overflow drain is just a piped into the top of the tank so the only way water is coming out of there is if the tank is full. 
    Or just open the fresh tank drain...If it is full, water will come out.
    And I didn't understand which blue pipe you meant in you post above, but having gone out and looked, you probably are referring to the fresh water tank overflow.
    Like @manyman297 said, there is only one way for water to get to that pipe, and that would be a full fresh water tank, unless your camper is plumbed completely wrong (which I doubt).

    2025 T@B 400 Boondock Black Canyon with 400Ah Battle Born and Victron Multiplus 3000
    2025 Honda Ridgeline Black Edition with Redarc Trailer Brake Controller
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  • manyman297
    manyman297 Member Posts: 1,433
    @ChrisFix Haha...or do that.

    It sounded like he tried that or maybe I misread and nothing came out? 
    2021 400 BD
    2020 Tacoma TRD Off-Road 
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  • ChrisFix
    ChrisFix Member Posts: 743
    edited August 2021
    manyman297 said:
    @ChrisFix Haha...or do that.

    It sounded like he tried that or maybe I misread and nothing came out? 
    I don't see anything that says they tried opening the fresh water tank drain - and I think you are on to the problem - that the tank is already full (maybe from dealer?).
    2025 T@B 400 Boondock Black Canyon with 400Ah Battle Born and Victron Multiplus 3000
    2025 Honda Ridgeline Black Edition with Redarc Trailer Brake Controller
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  • manyman297
    manyman297 Member Posts: 1,433
    Yeah, that has to be the problem...water is coming out of both ends and one end is "in" and one end is "out" so water is present in both ends. 
    2021 400 BD
    2020 Tacoma TRD Off-Road 
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  • Da_Birds
    Da_Birds Member Posts: 133
    Maybe the best thing to do at this point is open ALL drains until they run dry then close them and try filling again.

    I have a 2021 320CS and the rookie mistake I made trying to fill the freshwater tank the first time was that the water pump needed to be on to fill the tank, not just when using the faucets. I also then forgot to set it to dry camp after filling.
    2021 T@B 320CSS Boondock - "Chirping Bird"
    2018 Chevy Colorado - "Dad's Truck"
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  • ChrisFix
    ChrisFix Member Posts: 743
    @Da_Birds
    The 2021 400 doesn't need the water pump on to fill the fresh water tank. There is a "Power Fill" setting on the Nautilus panel that the CS doesn't have. It allows the fresh tank to fill directly from a fresh water hose source.
    2025 T@B 400 Boondock Black Canyon with 400Ah Battle Born and Victron Multiplus 3000
    2025 Honda Ridgeline Black Edition with Redarc Trailer Brake Controller
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  • Da_Birds
    Da_Birds Member Posts: 133
    ChrisFix said:
    @Da_Birds
    The 2021 400 doesn't need the water pump on to fill the fresh water tank. There is a "Power Fill" setting on the Nautilus panel that the CS doesn't have. It allows the fresh tank to fill directly from a fresh water hose source.
    Good to know! I suspected that might be the case because they call it "power fill" on the 400. That's why I just shared my experience with my 320 without directly suggesting that could be the issue with the 400. Hope I didn't cause any confusion.


    2021 T@B 320CSS Boondock - "Chirping Bird"
    2018 Chevy Colorado - "Dad's Truck"
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  • ESH
    ESH Member Posts: 27
    Appreciate everyone's feedback.  Oddly, the tank is not full, low point drain for the cold and hot water are closed, and yet the water gushes out of the blue overflow drain as soon as I initiate filling via the PowerFill or Siphon settings.  Did not have this issue at any point last Season (tank filled just fine).  Any other ideas?

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  • Dutch061
    Dutch061 Member Posts: 765
    We have a 2020 400 DBL, so I can't provide facts but the question that I always like to ask is "what changed"? If it worked last year, what has changed since then? I have no idea where you are located, did you winterize? Did you go through the proper steps this year after winterizing to prepare for use?

    Things like this typically don't just change out of free will. Something was changed or has been changed by someone and not put back to the proper function is my guess.

    Please don't read into this as an attack on you or anyone else, we (myself included) typically cause a lot of changes that result in most of our problems.

    Brad
    2020 400 BDL aka "Boonie"
    2022 Black Series HQ19 aka "Cricket"
    2021 F-250 Tremor with PSD aka "Big Blue"
    Concord, NC 
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  • jkjenn
    jkjenn Member Posts: 6,417
    Will you do us a favor and post photos of your Nautilys settings?

    2021 T@b 320 Boondock "Mattie Ross" | 2021 T@b Nights: 239 | Total nights in a T@b 455 | 2022 Jeep Grand Cherokee L Overland | T@b owner since 2014

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  • ESH
    ESH Member Posts: 27
    @Dutch061
    No offense taken.  My default assumption is "user error".  I winterized last year via air compressor (within psi tolerances) vs. antifreeze.  It has crossed my mind that perhaps something was dislodged/damaged in the process but I don't have a comprehensive enough understanding of the plumbing to know if that is even possible - and if it is - what could have happened (hence the post).

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  • ESH
    ESH Member Posts: 27
    @jkjenn
    Absolutely.  I am traveling and away from our Tab currently but will post upon return.  PowerFill valve settings are precisely as described on the unit itself, and cross-referenced against the manual.

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  • ChrisFix
    ChrisFix Member Posts: 743
    So the new information is that it used to work, but now doesn't...so like @Dutch061 says, something has changed.
    Anyone know how the fresh water tank inlet is plumbed? How could it be connected to the overflow outlet? This is a head scratcher to me...
    2025 T@B 400 Boondock Black Canyon with 400Ah Battle Born and Victron Multiplus 3000
    2025 Honda Ridgeline Black Edition with Redarc Trailer Brake Controller
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  • manyman297
    manyman297 Member Posts: 1,433
    I just filled our fresh water tank today for a camping trip this weekend. I was thinking of your situation as I was doing it and I just cannot figure out how that overflow could weep water without the tank being full. That overflow tube is directly connected to the fresh water tank as far as I know. Follow that overflow line inside (under the bed) to make sure it does indeed connect directly to the fresh water tank.

    And like @ChrisFix said, open the drain...and I'm not trying to be condescending as I'm sure you've already done this. Just want to make sure we're not missing something. 

    One more thing. I'm not sure how the Nautilus is plumbed but I wonder if there's something going on with a bypass valve or something. So somehow the inlet is bypassing the tank fill and redirecting its way to the overflow somehow? But I don't even know if that's possible. 
    2021 400 BD
    2020 Tacoma TRD Off-Road 
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  • BridgerSunset
    BridgerSunset Member Posts: 109
    Just a thought....is it possible your Alde drain (blue line in my pic, with yellow valve in open position) could be open after winterizing last year?  Not sure if the power fill setting allows this; nor if that's where your discharge is coming from.

    2021 T@B 400 Boondock  - Chev Silverado 2500HD 6.6L
    Montana USA


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  • ChrisFix
    ChrisFix Member Posts: 743
    @BridgerSunset
    I also thought about the Alde drains, but I'm pretty certain their drain tubes are clear vinyl, not blue pex...so I moved off that idea, but it is certainly worth looking at in this situation. 
    It really is the only drain valve that hasn't been discussed, and water will come out here when filling the fresh tank if they are open.
    2025 T@B 400 Boondock Black Canyon with 400Ah Battle Born and Victron Multiplus 3000
    2025 Honda Ridgeline Black Edition with Redarc Trailer Brake Controller
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  • Sharon_is_SAM
    Sharon_is_SAM Member Posts: 10,061
    Is the 2021 400 fresh tank overfill drain the same as the fresh tank vent?  If not, is the vent clogged?
    Sharon / 2017 T@B CSS / 2015 Toyota Sienna Minivan / Westlake, Ohio
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  • BridgerSunset
    BridgerSunset Member Posts: 109
    @ChrisFix
    Yeah, I checked & found the 2 Alde drain valves do indeed drain out clear vinyl tubes, as you described.  I thought maybe they were plumbed into that blue pex FW tank overflow line, but no.

    And on another note, on "powerfill to tank", water went directly into my FW tank & didn't come out the Alde drain, even though I had it open.  On "powerfill to fixtures", it came out the Alde drain right away.  I'm trying to understand all that too.


    2021 T@B 400 Boondock  - Chev Silverado 2500HD 6.6L
    Montana USA


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  • CharlieRN
    CharlieRN Member Posts: 438
    Da_Birds said:
    Maybe the best thing to do at this point is open ALL drains until they run dry then close them and try filling again.

    I have a 2021 320CS and the rookie mistake I made trying to fill the freshwater tank the first time was that the water pump needed to be on to fill the tank, not just when using the faucets. I also then forgot to set it to dry camp after filling.
    Don't want to hijack this thread, but I'm also a new owner of a '21 320(S - BD in my case) and have had difficulty filling the fresh water tank. Does this mean that even filling with the hose, you need to turn the pump on? I thought you only needed the pump if you filled from a bucket?
    2021 T@B 320 S Boondock / 2022 Telluride - Phillies/Eagles/Flyers Country
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  • ChrisFix
    ChrisFix Member Posts: 743
    BridgerSunset said:
    @ChrisFix
    Yeah, I checked & found the 2 Alde drain valves do indeed drain out clear vinyl tubes, as you described.  I thought maybe they were plumbed into that blue pex FW tank overflow line, but no.

    And on another note, on "powerfill to tank", water went directly into my FW tank & didn't come out the Alde drain, even though I had it open.  On "powerfill to fixtures", it came out the Alde drain right away.  I'm trying to understand all that too.


    @BridgerSunset
    Oh, that actually makes sense. "City water" is what I think you are referring to by "power fill to fixtures"...and that would indeed bypass the tank and just go to the fixtures...with the Alde en route to them, hence the draining.
    Makes sense the Alde doesn't drain when power filling the fresh tank, as it would need to be pumped from the fresh to the fixtures (again, with the Alde en route) for that to happen.

    2025 T@B 400 Boondock Black Canyon with 400Ah Battle Born and Victron Multiplus 3000
    2025 Honda Ridgeline Black Edition with Redarc Trailer Brake Controller
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  • bergger
    bergger Moderator Posts: 1,077
    Sharon_is_SAM said:
    Is the 2021 400 fresh tank overfill drain the same as the fresh tank vent?  If not, is the vent clogged?
    It does appear to be the same. I just filled ours today for a trip we’re leaving in Saturday. The overflow/vent is just behind the tire and flush with the bottom of the trailer. It’s not easy to see unless you duck under the trailer to look for it. When I fill our tank I can feel a lite breeze of air coming out of the pipe before water eventually comes out of it. If water is coming out of that pipe then the fresh water tank must be full. It’s not connected to anything else as far as I know. If it is coming out of the low point drain or alde drains then they are either open or possibly damaged from not using a pressure regulator. But it sounds like he is sure it is coming out of the overflow and not the low point or alde drains. And if that is happening the tank has to be full. 
    2021 T@b 400 BD  "Vixen Gail" 
    2018 Nissan Titan Pro 4X "Big Bird"
    Leadville Colorado
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  • ChrisFix
    ChrisFix Member Posts: 743
    Sharon_is_SAM said:
    Is the 2021 400 fresh tank overfill drain the same as the fresh tank vent?  If not, is the vent clogged?
    Or is the fresh water tank drain valve clogged or non-operational?
    That could create the scenario of a full fresh water tank, yet no draining when opened...
    2025 T@B 400 Boondock Black Canyon with 400Ah Battle Born and Victron Multiplus 3000
    2025 Honda Ridgeline Black Edition with Redarc Trailer Brake Controller
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  • ChrisFix
    ChrisFix Member Posts: 743
    bergger said:
    Sharon_is_SAM said:
    Is the 2021 400 fresh tank overfill drain the same as the fresh tank vent?  If not, is the vent clogged?
    When I fill our tank I can feel a lite breeze of air coming out of the pipe before water eventually comes out of it.
    Yeah, if you cover it with your finger while power-filling with fresh water, it will quickly develop a lot of pressure you can feel.
    2025 T@B 400 Boondock Black Canyon with 400Ah Battle Born and Victron Multiplus 3000
    2025 Honda Ridgeline Black Edition with Redarc Trailer Brake Controller
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  • Da_Birds
    Da_Birds Member Posts: 133
    CharlieRN said:

    Don't want to hijack this thread, but I'm also a new owner of a '21 320(S - BD in my case) and have had difficulty filling the fresh water tank. Does this mean that even filling with the hose, you need to turn the pump on? I thought you only needed the pump if you filled from a bucket?

    I started a new thread for this discussion:


    2021 T@B 320CSS Boondock - "Chirping Bird"
    2018 Chevy Colorado - "Dad's Truck"
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  • ESH
    ESH Member Posts: 27
    Thanks, all.  I really appreciate you pitching in to help.  Really is a mystery.  I wish I had an understanding of exactly how the FW overflow is plumbed.  Feels like there has to be some issue with the interface.  When I plug the overflow and try and fill with the PowerFill it seems to force some water into the tank (registers at about 1/3rd on the meter) but that is all I can get in there.  That is also more/less the volume that comes out when drained so I don't think the sensor is faulty. Ugh.

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  • manyman297
    manyman297 Member Posts: 1,433
    Keep us posted. This is really strange…but I bet once you figure it out it’ll be obvious (hopefully) to all of us.
    2021 400 BD
    2020 Tacoma TRD Off-Road 
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