Tank termination valve

[Sully]

What is the tank termination valve, they want it in the open position?

[topgun2]

When you use the tank flush port or waste water holding tank port, it will fill the black tank with fresh clean water.  Once the black tank is full (assuming that you continue to allow fresh water into this port) the water will fill the toilet.  Once the toilet is full it will fill your bathroom.  Once the bathroom is full ......

The tank termination valve is the place where the black tank terminates - i.e. the blade valve that you use to empty the black tank.  With this valve in the open position, the black tank can not fill thus the toilet will not fill nor the bathroom, etc..  Of course, you will not want to open that blade valve unless you have attached the waste water (black water - i.e. sewer water) hose (aka "stinky slinky") to your Oliver and the other end to an appropriate sewage dump.

Bill

[Sully]

Thank you for the detailed response 

[ScubaRx]

On 9/8/2023 at 3:32 PM, topgun2 said:

When you use the tank flush port or waste water holding tank port, it will fill the black tank with fresh clean water.  Once the black tank is full (assuming that you continue to allow fresh water into this port) the water will fill the toilet.  Once the toilet is full it will fill your bathroom.  Once the bathroom is full ......

The tank termination valve is the place where the black tank terminates - i.e. the blade valve that you use to empty the black tank.  With this valve in the open position, the black tank can not fill thus the toilet will not fill nor the bathroom, etc..  Of course, you will not want to open that blade valve unless you have attached the waste water (black water - i.e. sewer water) hose (aka "stinky slinky") to your Oliver and the other end to an appropriate sewage dump.

Bill

The following is only for those that have the regular toilet. Although those with "composting" toilets have their own list of issues, this is not on it and will be of little interest to them.

There is another scenario where the black water can fill the bathroom floor (and beyond) during the black tank flush and dump.

(cue the Twilight Zone theme music) ... Picture this, if you will...

You've hooked your black flush hose to the outside port and begun to fill your black tank in preparation for dumping. The black tank dump valve is closed as is the shower drain back-flow preventer valve. The black tank needs to be monitored during this step. I do it by holding the toilet flush valve open with my foot on the flush lever while peering down into the tank with a flashlight. Others may simply watch the readout for the black tank on the SeeLevel Tank Monitoring System. However you want to monitor the filling of the tank is largely irrelevant, but you do need to watch it. Consequences will occur if you do not.

Everything is running smoothly until a stranger appears at your door and is proclaiming to everyone within earshot that this is the coolest trailer he's never seen, where is it built?, what does it cost?, what is its weight?, how does it pull?, how do you like it? and on and on. Now you're distracted, and in trying to answer his questions, you forget that the black tank is filling with water. Ten minutes later you discover the bathroom has six inches of NASTY water in the floor, it is all around the base of the toilet and is now spilling over the threshold, out the door and into the main cabin.

But, it's not overflowing from the toilet, and you discover that the poop and pee is coming up through the shower drain. How could this happen? The black tank plumping is not connected to anything but the main drain and does not interface with the shower drain or gray tank system in any way so there's no possible way it could be doing this, right? But it is doing this. Nasty, Creepy, Perplexing but entirely possible once you understand how the bathroom is actually plumbed.

As the water level in the closed black tank rises, it can not escape into the toilet bowl because you’re not paying attention and the flush valve is closed. Neither can it escape down the drain because the black dump valve is closed. Pressure inside the black tank is beginning to rise also as the air trapped inside is being compressed by the rising water. At this point, I can personally advise you to NEVER depress the flush lever. If you wonder what will happen, go ahead and try it and report back here.

Now your black tank is completely full and the water has to go somewhere. The increasing pressure inside the tank will begin to push the water up the vent pipe that terminates through the roof from inside the closet. The same pipe is used to vent both the gray and the black tanks. What most do not realize is that this vent pipe also serves as the drain pipe from the bathroom lavatory into the gray tank. As the water level rises inside the vent pipe, it will eventually reach the connection between the drain and the vent pipes. The black water will now enter the drain pipe and, taking the path of least resistance, will flow down the drain pipe seeking entrance to the gray tank where it is stopped by the closed shower drain back-flow preventer valve. Now its only escape is up through the shower drain and out into the world.

Just when you thought you didn't have to worry about anything else.

[Townesw]

Pictures under the bathroom sink. When water in black tank can’t go out the dump valve it fills the black tank then goes up the black tank vent and down the sink drain to the grey tank if the back flow valve is open 

 

 

View looking down at top corner of black tank and sink drain going under shower

View looking at plumbing under vanity adjacent to inside of front wall

Path black water takes if black dump valve is closed and water is still filling black tank

 

When water from black tank fills the grey tank it comes up through shower drain. If back flow valve is closed it doesn’t fill grey tank but comes up through shower drain anyway. Either way nasty stuff. 

[ScubaRx]

3 hours ago, Townesw said:

Pictures under the bathroom sink. When water in black tank can’t go out the dump valve it fills the black tank then goes up the black tank vent and down the sink drain to the grey tank if the back flow valve is open 

 

 

 

when water from black tank fills the grey tank it comes up through shower drain. Nasty stuff. If back flow valve is closed it doesn’t fill Grey tank but comes up through shower drain anyway. Either way nasty stuff. 

Thanks Bill for the pictures. You perfectly illustrated what I was trying to put into words.

[Rivernerd]

13 hours ago, ScubaRx said:

You've hooked your black flush hose to the outside port and begun to fill your black tank in preparation for dumping.

Is there an advantage to filling the remainder of the black tank with water before dumping?  For the "Twilight Zone" reasons you so aptly described, I have always drained the black tank first, then left the dump (termination) valve open BEFORE connecting my "black water" hose to the flush port under the bathroom window.  Once the drain hose runs clear, I then disconnect the black water hose from the flush port, close the dump valve and then put the drain hose back into the bumper.

I have envisioned a spray nozzle inside the black tank which distributes the pressurized water input throughout the black tank flush port, which rinses the residual contents out through the drain hose.  Is this not correct?  Does filling the black tank before draining result in a cleaner black tank, even though that process risks the awful result you have described?

[ScubaRx]

7 minutes ago, Rivernerd said:

Is there an advantage to filling the remainder of the black tank with water before dumping?  For the "Twilight Zone" reasons you so aptly described, I have always drained the black tank first, then left the dump (termination) valve open BEFORE connecting my "black water" hose to the flush port under the bathroom window.  Once the drain hose runs clear, I then disconnect the black water hose from the flush port, close the dump valve and then put the drain hose back into the bumper.

I have envisioned a spray nozzle inside the black tank which distributes the pressurized water input throughout the black tank flush port, which rinses the residual contents out through the drain hose.  Is this not correct?  Does filling the black tank before draining result in a cleaner black tank, even though that process risks the awful result you have described?

If there is an advantage, it would be the greater volume of water to assist with the first dumping. 
 

As far as what CAN happen, I won’t allow someone to interfere with that process again. Once was plenty for me. I’ve always read that setting up or breaking down camp should not be interrupted. I’ve added dumping to that list. 

[Mike and Carol]

1 hour ago, ScubaRx said:

If there is an advantage, it would be the greater volume of water to assist with the first dumping. 
 

As far as what CAN happen, I won’t allow someone to interfere with that process again. Once was plenty for me. I’ve always read that setting up or breaking down camp should not be interrupted. I’ve added dumping to that list. 

If I’m under 50% I usually fill the black tank to 75 or 80% before dumping.  I then close the valve and fill it up again to 60 or 70%.  Then one more time, usually only about 50% and that dump is usually clear.  I’m usually outside and Carol is inside letting me know where we’re at.  If I do it by myself, I’m inside watching the level before going out and opening the valve.  Mike

[MAX Burner]

15 hours ago, ScubaRx said:

At this point, I can personally advise you to NEVER depress the flush lever.

Been there, done that, fully experienced the "mini-'Ol Faithful" right in the head (both of them)!

[MAX Burner]

@Townesw:  Outstanding visuals of a few of the key plumbing fixtures for the head - I'm breaking out my label-maker right now...  Thanks for the effort for posting that info - very helpful!

[mossemi]

I

9 hours ago, Mike and Carol said:

I’m usually outside and Carol is inside letting me know where we’re at.  If I do it by myself, I’m inside watching the level before going out and opening the valve.

This job is a lot easier with 2 people as Mike mentions, but if I am by myself I use a hose flow meter which are readily available at Amazon and hardware stores.  This allows me to monitor the amount of water that is flowing into the black tank.  I usually limit the rinsing fill to 12 gallons.  And as ScubaRx stated above, always ignore any interruptions from anyone!  Sometimes it’s OK to be rude.

Mossey

[MAX Burner]

17 minutes ago, mossemi said:

I use a hose flow meter which are readily available at Amazon and hardware stores.

Same here, Moss...  These work well, IMO.

[Steve Morris]

6 hours ago, ScubaRx said:

I’ve always read that setting up or breaking down camp should not be interrupted. I’ve added dumping to that list. 

One should never be interrupted while dumping. 🤪