Kitchen Sink Drain "Vapor Lock"

ChrisFix

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?

rh5555

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).

Denny16

If he had a hepvo valve on the shower, it would not allow water  back up past it (Hepvo valve) into the shower.

Bayliss

@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.

ChrisFix

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.

jimcenname

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.

Sharon_is_SAM

@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.

rh5555

@ChrisFix, the important question (at least to me) is:  Do you also have a Hepvo valve for your shower?

ChrisFix

@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.

TresK3

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?

Denny16

Not sure how good boiling water would be for the Hepvo trap valve.
cheers

jimcenname

I have warmed water in the microwave and washed it down the kitchen drain but I like the idea of baking soda and vinegar. 

TNOutback

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.

lhward

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.

Denny16

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 

dsfdogs

@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?

Denny16

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 

techietab

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.

rh5555

@Denny16: Where did you read about the boiling water / baking soda restrictions of the HepVo?  Having difficulty finding this...

Denny16

@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 

Robermcm

@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. 

ChrisFix

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.

subkron

@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.