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Kitchen Sink Drain "Vapor Lock"

So I was running the kitchen sink trying to fill my empty gray tank, as I wanted to flush out my rhinoflex drain hose.
The gray tank was initially empty as I was at a full hook up site with the gray dump valve open - and had forgotten to close it earlier in the day to capture water for dumping the tanks when breaking camp.
Once the gray tank registered 2/3 full, the sink stopped draining. The water did slowly drain out, but very very slowly as if the drain was clogged, which it isn't. 
I popped the gray tank valve and the sink drained and operated normally again.
I'm assuming I had some kind of a vapor lock situation - possibly due to the hepvo valve? Sure acted like it wasn't venting properly, but I don't understand why it happened like it did. I have in the past had the gray tank fill to the point it backed up in the shower...so I know it is capable of being completely filled.

Thoughts?
After two years of looking and considering...finally the proud owner of a 2021 T@B 400 Boondock!
2023 Honda Ridgeline RTL-E with Redarc Trailer Brake Controller

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    rh5555rh5555 Member Posts: 504
    If you remove the inspection panel below the bathroom door, what kind of trap do you have for the shower pan?  Our 2020 model has a traditional u-trap which would prevent a vapor lock from forming, what does yours have?  If it is another hepvo trap, then I could see how a vapor lock could form (especially if you were running water down the bathroom sink too).
    Roger and Sue Hill | 2020 T@B400 Boondock (Cryst@bel) | 2022 Land Rover Defender 110 - P400 | San Juan Island, WA
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    Denny16Denny16 Member Posts: 5,432
    If he had a hepvo valve on the shower, it would not allow water  back up past it (Hepvo valve) into the shower.
    2018 TaB400 Custom Boondock,  Jeep Gladiator truck, Northern California Coast.
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    BaylissBayliss Member Posts: 1,328
    edited September 2020
    @ChrisFix, I searched Google to see if there were any answers.  Although there are discussions of similar issues by RV owners, there is not much info regarding the cause (other than it being clogged with food, etc.)  There was at least one report I read of the membrane inside the valve somehow being forced/sucked in the opposite direction in the valve.  If you are not familiar with the correct installation and orientation of the valve, I would suggest checking that on the HepVO site and confirm that nuCamp installed it correctly.
    2019 T@B 320 S Boondock Lite2007 Toyota Tundra 4x4
    (Alde: 3020; Refrig: Isotherm Cruise 65 Eleg; Battery: BB 100Ah LiFePo4; Solar: Renogy 100Ah Suitcase; Victron BMV-712; Pwr Cntr: PD-4135KW2B; EMS: PI-HW30C)
    Greg & Marlene (Tucson, AZ)


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    ChrisFixChrisFix Member Posts: 728
    Thanks folks.
    The Hepvo valve looks correctly installed...and I've not experienced any issue with the sink draining until this afternoon - and it drained normally as soon as I opened the gray tank dump valve. And it wasn't a full tank issue as the shower pan is the low point that fills when the tank is full.
    I'm very vigilant about not letting any food waste down the drain...and I'm certain it isn't a clog of any kind, so a bit of a mystery.
    I'll email Creed and see if he has any insight on what happened and let you know if I find out anything.
    After two years of looking and considering...finally the proud owner of a 2021 T@B 400 Boondock!
    2023 Honda Ridgeline RTL-E with Redarc Trailer Brake Controller
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    jimcennamejimcenname Member Posts: 276
    I once dropped something in the kitchen drain on my 400 so I removed the valve to investigate. Wow was the drain slimy. I never put food if any kind or size down the drain yet it was slimy. I think the slime was mostly soap. I think my problem is I don't run water fast or long when rinsing. I'll probably clean the valve proactively.
    2019 T@B400
    TV: 2017 Nissan Frontier SV 4X4
    Southern California
    Full-timer since 2019
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    Sharon_is_SAMSharon_is_SAM Administrator Posts: 9,582
    @jimcenname - baking soda and vinegar will do the trick.  If you have never used it to clean a drain, be careful as it bubbles up a lot.
    Sharon / 2017 T@B CSS / 2015 Toyota Sienna Minivan / Westlake, Ohio
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    rh5555rh5555 Member Posts: 504
    @ChrisFix, the important question (at least to me) is:  Do you also have a Hepvo valve for your shower?
    Roger and Sue Hill | 2020 T@B400 Boondock (Cryst@bel) | 2022 Land Rover Defender 110 - P400 | San Juan Island, WA
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    ChrisFixChrisFix Member Posts: 728
    @rh5555
    I don't believe so. As @Denny16 mentioned, the gray tank wouldn't back up from the shower drain when it's full if it had the hepvo valve there. But I haven't taken the panel off to look under there.
    After two years of looking and considering...finally the proud owner of a 2021 T@B 400 Boondock!
    2023 Honda Ridgeline RTL-E with Redarc Trailer Brake Controller
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    TresK3TresK3 Member Posts: 65
    To @jimcenname's point: at home I often boil up tea kettle of water and pour it down the kitchen sink to help wash the gunk out.  Would there be any concerns with doing a similar thing in the trailer?
    2019 Tab 400 Boondock Lite
    2017 Dodge Durango AWD with Tow Package IV
    A can of Skyline Chili in the pantry
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    Denny16Denny16 Member Posts: 5,432
    Not sure how good boiling water would be for the Hepvo trap valve.
    cheers
    2018 TaB400 Custom Boondock,  Jeep Gladiator truck, Northern California Coast.
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    jimcennamejimcenname Member Posts: 276
    I have warmed water in the microwave and washed it down the kitchen drain but I like the idea of baking soda and vinegar. 
    2019 T@B400
    TV: 2017 Nissan Frontier SV 4X4
    Southern California
    Full-timer since 2019
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    TNOutbackTNOutback Member Posts: 633
    edited September 2021
    I just had this happen to me.  In prep for a trip next week, I sanitized the fresh water tank and ran some water through the lines.  The kitchen sink water would not drain.  I found this post while search for a solution.  When I went back out to the camper, the sink had drained.  Apparently one only has to merely look up a problem and it will correct itself!  ;)

    I still don’t know what caused it; maybe the membrane had just dried out with some aforementioned “gunk” in there and just needed to be wetted?  It is running now.  I think I will investigate some safe drain cleaner to use.
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    lhwardlhward Member Posts: 1
    When we fill our gray tank I have observed the sink drain backing and lower shower drain not. It has to be the HepvO trap failing to function when liquid backs up against its down stream side. I can not think of another possible explanation.
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    Denny16Denny16 Member Posts: 5,432
    edited September 2022
    Yes, we had the HepVo valve in the TaB shower allow water to backup into the shower, so in some situations with water in it on both sides, is will back flow.  

    As for putting boiling water and/or baking soda down the drain with a HepVo valve, it is not recommended, as the heat from boiling (warm/hot is OK) water may damage the membrane in the valve.  Unlike a traditional drain trap, Food particles do not back up and collect in a HepVo vale, they flush through it.
     Cheers 

    2018 TaB400 Custom Boondock,  Jeep Gladiator truck, Northern California Coast.
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    dsfdogsdsfdogs Member Posts: 595
    @Denny16 so with the HepVo valve, if you aren't supposed to pour boiling water down the drain, what do you do about draining boiling pasta water, for example?
    Debbie in Oregon
    2023 Tab 400 / 2022 F150 XLT Sport 3.5EB
    Traded in - 2018 T@B 320 S/2019 Toyota 4Runner SR5

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    Denny16Denny16 Member Posts: 5,432
    edited September 2022
    I would pour it into a wash basin, and let it cool a bit first. That said, I use an outdoor cooker to boil water needed for pasta, corn, etc — to keep steam out of the TaB.

    All of the plumbing in a TaB is PVC and ABS pipes, some of which which are glued in.  Also the HevpO valve has sealants in its construction.  I found this bit of advice from a plumbing site on line:  
    To address one of the most common trends when unclogging a drain at home- is it safe to pour boiling water down the drain? Though you may find mixed answers to this question, experienced plumbers strictly advise against this action. In most houses, there are PVC pipes under the sink- If you have a newer home there is over a 75% chance your pipes are PVC. These pipes have the capacity of withstanding intense heat, but not as high as that of boiling water.”  
    Cheers 
    2018 TaB400 Custom Boondock,  Jeep Gladiator truck, Northern California Coast.
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    techietabtechietab Member Posts: 161
    dsfdogs said:
    @Denny16 so with the HepVo valve, if you aren't supposed to pour boiling water down the drain, what do you do about draining boiling pasta water, for example?
    Drain into a dish washing basin (there are about a zillion space-efficient collapsing types available from online retailers like Amazon) instead of the sink, and let it cool. Dump down the sink if you must, but you're probably better off walking that carbohydrate-heavy water over to a campground sink/toilet than letting it ferment in your grey tank.
    Northern VA
    2022 T@b 320 S / 2021 Subaru Outback
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    rh5555rh5555 Member Posts: 504
    @Denny16: Where did you read about the boiling water / baking soda restrictions of the HepVo?  Having difficulty finding this...
    Roger and Sue Hill | 2020 T@B400 Boondock (Cryst@bel) | 2022 Land Rover Defender 110 - P400 | San Juan Island, WA
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    Denny16Denny16 Member Posts: 5,432
    edited September 2022
    @rh5555, I found several references, most of which are more to do with PVC plumbing, which a HevpO valve is made from.  
    Here is one: https://callfourseasons.com/is-it-safe-to-pour-boiling-water-down-the-drain/
    Another:  https://drainmaster.com/industrial/product/hepvo/ 

    Whilst the last one discusses installing and maintaining the HepVO valve in a video.  Whilst it does not directly address boiling water, it does discuss the maintenance free features of the HepVO valve and that it does not clog, thus does not require soda and boiling water to clean or unclog.  To clean a HevpO valve, simply remove it (easy to do and it is held in place with threaded fittings that unscrew) and clean it with fresh water, a hose with a spray attached works quite well.  It is the back side that gets dirty sometimes, and the in,ynway to clean this is by removing the valve.  Running hot or cold water down it may not always flush out the back side around where the membrane seals to the PVC body of the valve.  
    Cheers 
    2018 TaB400 Custom Boondock,  Jeep Gladiator truck, Northern California Coast.
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    RobermcmRobermcm Member Posts: 87
    edited June 5
    @chrisfix, did you ever sort this out?  I’m having the exact same issue on a 2023 400 bd. Sink works fine until grey tank is about 2/3 full.  Then is crawls. 
    2023 Tab 400
    2015 Audi Q7 TDI
    Northern Ohio

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    ChrisFixChrisFix Member Posts: 728
    Robermcm said:
    @chrisfix, did you ever sort this out?  I’m having the exact same issue on a 2023 400 bd. Sink works fine until grey tank is about 2/3 full.  Then is crawls. 
    I just gave the valve a few solid taps with a screwdriver handle and it hasn't been an issue since then. Good luck with your setup.
    After two years of looking and considering...finally the proud owner of a 2021 T@B 400 Boondock!
    2023 Honda Ridgeline RTL-E with Redarc Trailer Brake Controller
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    subkronsubkron Member Posts: 152
    @Robermcm & @ChrisFix I just had the same issue come up yesterday!  We had been boondocking Wed-Sunday when wife indicated the sink was getting slow to drain.  I knew we were more than half-full in the grey tank and I really didn't think much more of it other than possible vapor lock. The camper was pretty much dead level, right-on side to side and 0.25" high in front ( that darn Beech Lane leveler is nice).  We came in late last night so tanks were not emptied. If I can remember I'll dump in a half gallon and time it. Then drain the grey and repeat.  If I had a way to get a real idea of tank liquid volume/level I could repeat at different grey tank levels but those KIB indicators are relatively useless.
    2022 T@B 400 Boondock
    2015 RAM 1500 Outdoorsman Quad Cab
    South Jersey
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