Water entering gray water tank under pressure

Denny16 · June 2021

Sharon, I do not know about the 2021 TaB400, but on our Jan 2018 build, no overflow opening at or near the top of the gray tank. We overfilled it once, and the gray water backed up in the shower, sink drain was slower working also. No water draining or dripping from the bottom either. When I drained the tank, shower and sink drained normally.
cheers

ScottG · June 2021

I'm skeptical (though far from certain) about the installation of an overflow drain on the gray tank. Assuming the tank is otherwise properly vented, there would be no functional reason for this.

The only advantage would be that clueless owners could happily overfill their tanks without stinky gray water backing up into the shower. However, that means nuCamp intentionally included a system for spreading said extra gray water all over the ground--an unlikely scenario.

While I don't doubt that some have experienced what appears to be an overflow situation, I'm wondering if the root cause isn't an unintended leak at some fitting near the top of the gray tank.

Verna · June 2021

I’m skeptical about “an overflow opening” on the gray tank because of the many EPA rules and regulations that would violate.

—changed quoted term to be in line with the actual description” of the problem. Verna

ScottG · June 2021

@Verna, I assume you mean you are skeptical about an overflow opening. The gray tank needs an atmospheric vent or else it would neither fill nor drain properly. However, atmospheric vents are typically higher than the top of the highest fixture.

Verna · June 2021

Thank you, @ScottG.

ScottG · June 2021

Not trying to be nitpicky, but there seems to be a number of competing ideas about how the gray tank on the 400 is actually plumbed, and the specifics seem relevant in this case.

I would not be surprised if there were manufacturing standards that prohibited the installation of an overflow given the potential for violating those EPA regulations. Not to mention the "ick" factor when you're the next camper on that site! ;-)

rh5555 · June 2021

According to Raphael at NuCamp, there is not an intentional overflow opening at the top of the grey water tank; it should just back up into the shower pan. Many people have attested to the fact that there is an opening, as the excess grey water drips out under the TAB, and the shower pan doesn't fill.

I can only assume that NuCamp endeavors to seal all the plumbing openings into the grey water tank but don't always succeed, or that some connections shake loose after delivery. Hence different owners have different experiences.

If you want to know which camp you are in, fill your grey water tank through a garden hose into your shower pan till the shower pan has an inch or two of water in it. Then wait. If the level goes down and you have a puddle under your trailer, you have an unintended leak. This might be a warranty issue if your TAB is young enough.

Denny16 · June 2021

rh5555 said:

According to Raphael at NuCamp, there is not an intentional overflow opening at the top of the grey water tank; it should just back up into the shower pan. Many people have attested to the fact that there is an opening, as the excess grey water drips out under the TAB, and the shower pan doesn't fill.
I can only assume that NuCamp endeavors to seal all the plumbing openings into the grey water tank but don't always succeed, or that some connections shake loose after delivery. Hence different owners have different experiences.

I agree with you on this Verna and rh5555, no need to have two vents. If you look at some of the TaB 400 assembly line videos (Paul the AirForce Guy) you can see the holding tanks vent connection pipe. Both black and gray tanks are connected to a single ABS vent pipe running up behind the closet in the TaB400 and exiting on the roof.
cheers

Fiddlinmike · October 2023

What ever happened with this mystery? Tinnitus describes a situation where his grey water tank filled with city water though he contends that no water ever came from an internal faucet (sink or shower). The group seems to believe that is impossible. Is it impossible to fill a grey water tank except through sink and shower drains?

Also, the group seems to believe NuCamp is accurate in saying there is no design for grey water tank relief (apart from air venting). That means overly full tanks will only result in water coming up from the shower drain and not under the trailer unless there’s a line break somewhere.

Here’s why I ask. A couple of days ago I awoke to a full grey water tank that was most certainly not the result of conscious use. I was on city water. I disconnected on discovery and drove to a dump station with water streaming from the bottom of my 320 the whole way.

In my case, I believe I know the cause. The valve on my toilet feed was open slightly. The bowl filled and ran over into the shower drain, slowly but for hours. Still, I’m looking for confirmation that there’s no other possibility (no leaks from the kitchen sink faucet- I’m sure.)

The mystery of under trailer leaks remains. I’m going to post about water pressure on another related thread.

ScottG · October 2023

@Fiddlinmike, I'm not aware of any resolution or further information on this issue, but I'm stickin' to what I (and others) said previously in this discussion:

There is no intentional connection between the fresh water supply and grey water tanks.
The only openings to the grey tank are the fixture drains, the atmospheric vent, and the dump valve.
There is no grey tank "overflow" other than the fixture drains and the atmospheric vent.

I'm not claiming anyone is imagining this problem, but something else needs to be at play here. Possibly a break or disconnection somewhere, or (highly unlikely) someone made an extreme error during plumbing assembly.

I agree the toilet overflow is the mostly cause of your grey tank filling up. The leak is a little more mysterious. Assuming it's related to the overflow (and that is an assumption) I'd guess (and it is just a guess) a crack in the grey tank itself, or a leak at one of the connections between the drain system and the the tank.

So this remains a mystery. Please keep us posted on anything new you discover.

BrianZ · October 2023

@Fiddlinmike
You may want to take a look at the 3-part video by Mark on fixing & preventing shower drain leakage by Mark..

https://youtu.be/OSmotwjvuGo?si=M0xSDBi8DLJutd8E
It could explain your leakage from underneath & how to fix it.

BridgerSunset · October 2023

Reading back through this thread made me wonder about this:

The black & gray tanks each have vent lines that are tied together prior to exiting the roof. If that roof vent is blocked in some fashion, then trapped gas or air pressure will negate normal draining concepts, since balance & liquid heights are thrown off. This may allow fluid columns to rise higher than normal gravity would allow, such as at the sink. Not sure how the Hepvo works in gas or in an elevated pressure imbalance.

Would also explain the gushing when dumping the gray tank. Could the tanks not be full of water, but rather gas under pressure, caused by heat and/or decomposing sewage?

Further, if the black tank flush system is for all intents tied into that same blocked vent line, couldn't all tanks (gray and black) backflow out to the Nautilus area & emerge from that flush connector? This part is a little more problematic to rationalize, but still possible.

Or not ?!

ScottG · October 2023

The vent is a pretty big diameter PVC pipe, but yeah, if it were somehow completely blocked it could cause some strange happenings with regard to draining.

And while I don't have any first hand knowledge of the Nautilus, I suppose what you suggest regarding the flush system is theoretically possible (if not all that probable).

Fiddlinmike · October 2023

Thanks, @ScottG and @BrianZ. I’m pretty sure you’re right about full-tank leaking coming from cracks or breaks somewhere, not by connections. I have pieced together a little about the strange problems I had with filling the tanks in the first place which I’m going to post shortly.

GTfreefall · May 22

Tinnitus said:

Here’s the set-up: 2020 T@B 400 that I've had and used for more than a year. Three-night stay at a full-hookup RV resort. Water hose and brass in-line pressure regulator that I’ve been using for a year without issue hooked up to the resort water system, with the regulator, of course, at the source end of the hose.
We had one night at one site. Our only water use was to wash a few dishes in the evening and the next morning for two people. I emptied the gray water tank the next morning. and did not notice anything unusual.
So, on to the second campsite, same RV resort, for nights number 2 and 3. Same deal. Water usage confined to washing a few dishes for two evenings and one morning for two people. (Showers, toilet, etc., at the resort’s very nice bathhouse.) I did not empty the gray water tank on the first morning at the second site, because I’ve never had to do it daily for this kind of usage in the past. The gray water tank had previously never came close to being full after two days of light dishwashing.
At around 4:00 am on the second night in the second site (third night of camping), my wife awaked me and said she could hear “gurgling”. Once awake, I could hear it, too, coming from the right rear area of the trailer.
I got up, lifted the lid of the kitchen sink and found it full of water, just shy of the top. (The sink plug was being stored in the cutlery drawer.) I lifted the faucet up and determined that no water was coming out of it, and the faucet handle was in the full closed position.
There was a small amount of water puddling up from the drain in the shower, but no water was flowing from the shower head or the shower sink faucet, and both handles were in full closed position.
I went outside with a flashlight and found water dripping onto the ground from the right rear of the trailer.
I immediately turned off the resort water at the tap and the sound of the gurgling inside the trailer stopped.
I opened the valve for the gray water tank and it was like releasing Niagra. Never, in my year of owning this trailer has there been that much water flowing out of it, and as I said, this was after a mere two evenings and a morning of light dishwashing.
The kitchen sink drained itself with the emptying of the gray water tank. And remember, the sink is much higher than the floor of the shower. The puddled water in the shower never came near the edge of the pan.
Okay, so with all faucets in the full closed position, water was entering the gray water tank to the point where a column of water rose up into the kitchen sink (but not over the edge), and was leaking out into the body of the trailer somewhere. (I went over every place I could access with a flashlight, but I can’t figure out exactly where that leak was.)
How did this happen?
What should I look for?

I experienced the same thing in my Forest River RV. Hooked up to city water to drain, noticed low water pressure while cleaning lines. Came back 10 mins later to have water overflowing out of my tub and running out back corner of the camper. Dumped the Grey quickly and shut off the main water line connected to city water inlet. Posted on forums for help, and everyone stated it was impossible. Not impossible, I witnessed it plan as day.

ScottG · May 23

@GTfreefall, thanks for weighing in. I don't think anybody is doubting what happened, but rather just saying that whatever is behind it needs to obey certain basic laws of physics. Water does not self-generate (at least not in this case...), nor does it teleport from one closed container to another.

So, that said, did you ever figure out the root cause the problem you had? Did it reoccur after that one incident? We don't argue much over what happened, but we do tend to fixate on why. :-)

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