Tab 400 BD Black Tank Flush leak

mjwaldner

My Leake was due to the fitting under the bathroom not being tightened all the way. 1/4 turn fixed the leak for me. But I always blow this out during winterizing.

Denny16

@qhumberd, the Balck tank flush doe not retain any water after it is used.  Water on the black tank side of the valve should drain into the tank, water in the line between the hose connection and check valve will drain back out the hose connection.  Blowing it out from the hose connection won’t hurt, and ensures the line does not have any amounts of water that would cause freezing damage.  Since this is an open system, any water left inside has space to expand inside the water lines.  

Cheers 

bergger

stmur7 said:

OK. So I removed the panel that was below the sink and turned the black water flush on. The leak was pouring down from behind the whole sink panel. I removed all screws to take of the sink but there are 2 right behind where the sink rotates up and down that I can't get to. It's a #1 square screw but they put it in a spot that no screw driver can fit. Hard to believe they put the screws in that spot. I'm not sure how to get to them. Seems i need some kind of really small right angle type of screw driver that takes up almost no length coming off the screw. If anyone knows what I mean, please let me know how you did it or what you used. I will say I am thankful to you folks who helped me with this. It looks like it is that check valve if it's up higher above the sink behind the panel. Why it goes up there for a blackwater flush is a whole other question.

Get a micro ratchet set.  They are compact and not very expensive and just make sure you have the proper size square bits for the trailer.  I keep on in the trailer and have used it to remove the cover over the Alde piping in the bathroom.  There is also no room for a screw driver if you want to remove that to get to the bleeder valve.  

stmur7

OK. So I finally got the whole panel off and it the hose going into the check valve was completely loose. Just high speed shoddy labor during assembly at the factory. I tightened it up and good to go, but gosh, it shouldn't be so hard to get at screws. I left them out because they really aren't necessary in case I need to get back there again. This forum is awesome! Denny and the rest of you have been such a big help. Thanks!

Denny16

You are welcome, glad it got sorted.
 Cheers 

qhumberd

Denny16 said:

@qhumberd, the Balck tank flush doe not retain any water after it is used.  Water on the black tank side of the valve should drain into the tank, water in the line between the hose connection and check valve will drain back out the hose connection.  Blowing it out from the hose connection won’t hurt, and ensures the line does not have any amounts of water that would cause freezing damage.  Since this is an open system, any water left inside has space to expand inside the water lines.  

Cheers 

This is what my logic was saying as well since the hoses to and from are vertical. But after reading about these leaks, which appear to be only loose connections, I was concerned that the one way valve could trap some water. It’s a lot of work to get to this spot. Good to know blowing from the hose side is not a problem to the valve. Glad all got their leaks fixed!

Denny16

I I would use low pressure air, not to exceed 30-40 psi, you need air volume, not pressure to flush the water out of the lines.  I use a nail gun compressor, but a 5-gallon portable air tank with a regulator on it set to 30-psi would also work. Cheers 

Mack

Hello, we are new to the forum and just picked up our new 2022 Tab 400 Boondock in June. First time running water through outside black connector to flush black tank and we got a flood under front left seat where the AC unit is. 

I looked under the bed and it is all dry. Also all dry on shower floor and under shower sink. I’m guessing leak is maybe where flush line goes into top of black tank? However I don’t see any panels or any easy access to the black tank to have a look. 

Any thoughts or help would be much appreciated.

Sharon_is_SAM

@Mack - I moved your post to this thread which details your issue.

qhumberd

Wow, I hope this is not a pattern for the 2022 production run. If a 1/4 turn on the back flow valve connection is the issue, it’s going to take a fair amount of labor time just to snug those up.

Jake_Elwood_and_us

I don't have this leaking problem on my 2021 400 but I did remove the lower access panel below the sink just to get familiar just in case. As I was looking at it I thought I would just cut the lines just below the plywood and reinstall a new back flow check valve in front of the plywood. Lots of access and makes life a whole lot simpler than removing the entire sink assy.

Denny16

The black tank flush connections are not a widespread problem, but started croppi;g up on some late 2020, 2021 and now a few 2022 TaB400s.  The original issue was the check valve being hooked up wrong way round, causing back pressure leaks, lately it is the connections to the check valve being loose.  

I agree getting to the check valve is not easy, and nuCamp should have a pre-shipment water system check area, to hook up water to the systems for a final check for leaks and issues, including the black tank flush, since there have been numerous issues.  Also, this should be one of the things dealers should check as part of their trailer delivery prep. 
 Cheers 

Mack

One month in we had to return our T@B 400 Boondock for warranty repairs. Water inside every time we tried to do a black tank flush. 

Turns out the black tank flush line check-valve failed, but also a crimp on a joint in the flush line was not tightened enough and ended up leaking. 

Just wondering if anyone else with a 2022 model has had any similar issues and knows of an easy way to access the plumbing.  If i could have accessed the problem area, probably could have made those repairs myself, rather than making the four hour drive (one-way) back to our dealer for warranty work. 

No issues with dealer they were excellent and we still love the trailer, but in such a premium well-thought out trailer, I can’t understand why all plumbing does not have easy access…

qhumberd

When I review the various factory build videos it is apparent that the plumbing and heating lines are all exposed until the sides and roof are applied. The items in the way are the freestanding cabinets that are mostly tied together. Having said that, the primary plumbing access points are the toilet, the kitchen sink and the folding bath sink. The outdoor shower is a self contained unit. Alde plumbing is easier access outside service door or under bed in the 400. The black tank flush system is an anomaly since I think it is designed to last the life of the trailer. Therefore access shouldn’t be needed. PEX connections are allowed to be behind closed walls in homes when installed correctly.

I had to remove my round folding sink and it was not that hard and certainly less time than a 4 hour drive. Your square sink may be mounted slightly differently. See this thread for pictures of the area behind sink and the black tank valve.

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

All this to say that I read a lot about leaking PEX here. It seems reasonable for someone at the appropriate stage of build to pressure check the plumbing fittings before walls and roof go on. Dealer could too but if a hidden or covered connection leaked it could be missed. I am not sure those that install the PEX lines are licensed plumbers, and without practice it is easy to make a crimping mistake.

Just my 2 cents, now inflated to 3.5 cents.

qhumberd

Denny16

The water lines are pressure checked for leaks and loose connections after they are installed (before outside walls are installed.  But the issue is there is no real way to pressure check the black water flush system, as it is an open end sprayer setup.  A quick pressure check, however, would show a reversed install (or failed)  check valve, but not a loose connection.  

Cheers 

Mack

Thanks for the info guys! I think it was someone making a crimping mistake and a bad check valve that just failed. The front of our sink area is different then in that other form. It has an accessible hatch below the sink, but when I opened the hatch I couldn't see where the leak was happening and decided it was best to let the dealer fix under warranty. 

Denny16

That is always a wise idea, and is why you have the warranty. 

Cheers 

qhumberd

Denny16 said:

The water lines are pressure checked for leaks and loose connections after they are installed (before outside walls are installed.  But the issue is there is no real way to pressure check the black water flush system, as it is an open end sprayer setup.  A quick pressure check, however, would show a reversed install (or failed)  check valve, but not a loose connection.  

Cheers 

This is good to know and helps me like NuCamp even more. If we ever get to take a trip there and get a factory tour I know I'll learn a lot. Also right that the black tank flush never fully pressurizes so a bad PEX crimp might not leak much anyway since it is only hooked up briefly. Except when installed backwards. Sounds like the newer sinks on the 400 are more involved to remove.