400 fold down sink not draining well

BigGrover

@Tabfortwo, yup and in the pics it looks like your sink doesn't take up any more room than the folded sink

Tabfortwo

It sticks out 8.5 inches from the wall the OEM was an inch smaller. So not a significant difference. 

falcon1970

OK, we all agree the original fold away sink is not very good.  Does nuCamp have a suggestion for improving the drain function that doesn't include a $500+ replacement?  It is apparent that the drain is way undersized.  Any suggestions for putting a larger, smoother drain in?

COHiker06

There's no air vent at the sink to break the water pressure above the drain. Bathroom sinks have an overflow/vent in the basin but the sink in the 400 doesn't. If a breather can be plumbed in to the sink drain it should flow faster.  Now I just have to figure out how to get to the attach point just below the drain hardware.

treefrog

Kitchen sinks have no overflow.  Probably just too small of an opening at the stopper.

Tabfortwo

It's a very poorly designed set up. There's no vent and it drains through a 5/8 Id couragated pipe.

gspdx

It is a poor design.  At this point I am not interested in a mod though.  I added a hook to the wall and keep a cloth hanging there that I can wipe the sink out with.  Then hang it back up.  It's really not a big deal.  I guess we pay the price for being "early adopters" of this folding sink design.

But I doubt I am done.  Might pull the sink off at some point a do some investigation. 

It would be nice if Nucamp provided some other options, even if it is to purchase a retrofit kit to open up the drain.  I would be interested in that.

Tabfortwo

Mine is a 2018 and they have since replaced it with a square sink. This has not fixed the issue though. 

rh5555

I know this is off-topic, but we cannot help noticing a lot of pre-2020 TAB400 owners commenting here.  We'd like your opinion on the functioning of the CoolCat air conditioner in our poll, please.  Thank you!

Tabfortwo

For the amount of times I've used it. It does a very good job.  I've used it in 110 degrees but low humidity. 

N7SHG_Ham

@Tabfortwo really? I thought the square sink was the cure?

Tabfortwo

Not from what I was hearing at tabazona. 

driftless

We had our round sink replaced with the square and had no issue at first then the trough drain plugged.  The reason it plugged is how the drain was plumbed.  The photo is of how the trough drain was installed.  We plan on changing this by installing the Hepvo drain to the tank vent line.
HEPVO 1-1/2" Trap https://www.amazon.com/dp/B00NLMPLDU/ref=cm_sw_r_em_apa_i_9ETmEbTCFMXF0

Denny16

A Hevpo trap appears to be about 9-inches long, so you would need at least 10-inches between the sink sump where the PTrap is and the floor drain.  Not sure you have enough room per the posted photo.  NuCamp is usin the Hevpo trap on the galley sink in the Nuer models of the TaB 400, and I plan to change mine to a Hevpo trap.  

I used to work on sailing boats in the 18-40 foot category, and most small boat galley sinks use a 3/4 to 1-inch drain, so slow draining basins is a fact of life in these small boats.  A bathroom sink is normally a low use sink with minimum water, and expecting a small RV basin as used in the TaB to have the same performance as your home sink is not realistic.   The 3/4 or so drain hose at the bottom of that trap setup, is the bottle neck, and can be prone to clogging too.  Your home bathroom drain is 1.25-inch, and it’s PTrap gets plugged with hair and debris quite easily, so a smaller drain is even more likely to have issues.

The folding sink does not drain directly into the trap, it drains into a cistern on the wall (the tray the PTrap is connected to, so adding a larger drain hole,to the sink (the change in the square sink) allows it to drain faster into the cistern drain tray, but this rate has to match the drain rate of the lower tray, or it can overflow.  This is a very old design used in railway coaches in the late 19th century and early 20th Cent.  Their, the basin was just tipped back into is vertical position and the water just drained out the back into the cistern tray to drain down the exit tube (normally on to the tracks and later to a holding tank).  Small yachts of the same era copied this design.

The original owner of my late 2018 TaB 400 solved this issue by not having the bathroom (Head) sink installed in the first place.  Having two sinks in a small trailer (or boat) is somewhat redundant, and I think unnecessary, where one larger galley sink can suffice.
Cheers.

rh5555

I took this access panel off my 2020 TAB400 last fall and am pretty certain that they used 1.5" piping all the way through this area.  I certainly don't remember seeing that bit of corrugated pipe.  I don't think any clogging issues will be cured with a Hepvo trap (not that they aren't great!), I think the 1.5" black abs piping needs to be extended all the way to the grey water tank.  Looks like you got half an upgrade to me!  BTW, a Hepvo trap can be mounted horizontally, so there would be room.

falcon1970

An additional issue with the round sinks is that (at least on mine) the drain stands slightly higher than the bottom of the basin.  No matter how large the drain hose is water still ponds in the sink since it can't get to the drain.  Closing the sink will allow the water to slosh from the basin to the cistern but if you aren't careful it will also slosh out of the cistern and down the front wall below the sink.

Verna

The square sink did cure the draining problem in my 2019 T@B 400. 

Why mine works and others don’t is beyond me. Maybe I don’t turn the faucet on as high as others because I’m always very conservative with my water usage while camping since I Boondock so much. 

qhumberd

Our 2019 T@B400 fold down round sink had to be removed when we accidentally removed the small drain plug and the corrugated pipe pulled away never to be seen or felt again. I was surprised at the difference in the pictures of the different 400s and the plumbing variations in this location. We are going to cover over the sink area and add small towel bars and a small shelf but thought I would share these images of why our sink drained so slowly.

This first shot is after removing the sink and the supply and drain lines. The sink drained via 2 corrugated 3/4 lines that connected at this T and then went down to grey tank. I presume there is trap below this behind the outdoor sink as I have seen in other photos, as there is no trap here.

 

This is the back of the round sink showing the toilet riser supply lines to the faucet and the two corrugated drain lines. The straight one from the basin behind the fold up sink itself and the one seen on the R comes from the sink drain itself and had gotten loose from  the sink bowl when the pop up came loose. I could see why it drained so slowly. Tipping back and forth just gave me something to do while waiting. This design was never going to work well and would have eventually have plugged. Not sure how the square sink differs from this design



Will add some more as I start a thread after I get this done. Have not decided how I want it to look but thanks to those that have posted pictures of their new sinks and sinkless bath walls for ideas. I really helped me understand how to take this down for someone who is a novice. BTW no way I would pay to have this replaced without changing this plumbing arrangement. One positive note I will add is that the area was clean with no assembly debris etc and the cabinets are tight and put in with very close tolerances plumb and square. Excellent craftsmanship there all around. Just a bad sink design.

jimcenname

Solved the bathroom sink problem on my 2019 400 this way. 

qhumberd

So @jimcenname it appears your plumbing behind the wall is similar as the corrugated drain in yours is just a bit beyond the vertical of the plywood support behind your panel. My wife saw yours and clearly wants towel bars in our bath for more drying space. We are thinking a small shelf near the bottom that will come out  about 3 inches to the edge of the plastic cover below and might be useful. Similar to the mod that @Kevin@7 did but a bit lower on the panel and squared off.

bellimages

Tabfortwo said:

Mine is a 2018 and they have since replaced it with a square sink. This has not fixed the issue though. 

a square sinks in a small bathroom takes up too much room. I LOVE the design of our 2018 Tab 400, including the sink. I just wish there was a solution to the slow drain. I'm willing to live with it, because I like the look of it. 

qhumberd

From taking mine apart I was convinced that without plumbing skills I do not have, it was just going to continue to be a problem. We have used it a couple of years with a small shelf and towel bars and have not missed the fold down sink at all. In fact, it has noticeably more room when using the shower. 



Here is my arguably long post on taking out the sink that shows the plumbing better and maybe someone has a better solution to the drain problem

https://tab-rv.vanillacommunity.com/discussion/15361/t-b-400-bathroom-folding-sink-removal-add-panels-and-shelf#latest