Black tank flush - valves always open?

I often close the black tank drain for a couple of minutes when rinsing the tank. Just another way of adding water to the tank. Its easier to add water with the "Tornado" when finished rinsing than going inside and filling the toilet bowl several times. Just don't get distracted and wander away.

In any case, my bathroom sink is plumbed into the black tank providing an alternate vent should the real vent get blocked.

On the plumbing diagram for my MH, side view shows the tanks and plumbing including the vent line. The "flood test" is shown by solid line at 24 inches above the two tanks.. So apparently they actually test that the system will hold water.

At KOA in Myrtle Beach some time back, MH next to me had toilet back up inside the rig. He had dumped and was rinsing the black tank with a "hold open" collar in the toilet valve to keep the water running....and it did.

Personally seen it with my own eyes. Sewage coming from vent on top of a 5th wheel. He was flushing and talking, what a mess.

My good friend flooded sewage out of the bathroom down the steps into the living area not 1 time but 2 times the first year in his brand new 5th wheel. Wife almost killed him twice.

Me I do not flush just dump and add water. Never have had a problem in 20 + years. 1 trailer, 2 5th wheels and now a MH.

Reddog1 wrote:
I am a bit confused. The black tank has at least one vent. The toilet has a flapper that is sealed. If it were not sealed, waste odor would be in your RV. How could you flood the inside of your RV with black tank waste?

With the gray tank, the "P" traps only have a water seal. You can flood your TC with gray tank waste.

Wayne

Wellll- try it - and I guarantee you will NOT like it. The 'flapper" valve may not hold against the pressure. Has happened to several on this forum.

NEVER leave beside the dump valves while using the flusher!! As others have said, I flush then close the dump valve for about 2 minutes and then open it. Do this twice (or more) until only clear water comes thru. Then close the dump valve and hurry to the stand pipe and turn off the water. This leaves a few gallons in the bottom of the tank. But - I repeat -- DO NOT LEAVE while dumping/flushing!

vic46, very true. I forgot that some RVs are plumber that way. You could poop in your RV.

Wayne

IAMICHABOD wrote:
I have to agree, the only way out for the water is up and out the vent tube if it gets too full. Now that may be a mess but I see no way it will flood the inside of the RV unless the toilet flapper is not seated.

Whoa!!!!!!!!!!!!!!!! It is not uncommon for other water use sources to be connected to the black tank rather than the gray. Two reasons for this is firstly to try and balance the storage load between the two tanks and secondly to insure that adequate water is getting to the black tank. If the toilet valve holds the back flow, which I doubt because of the pressure, another waste water source is likely to do the flooding. As an example the outflow of our vanity in our head is plumbed to the BLACK tank.
Vic

40 gallons can flow through a garden hose in very little time. Getting distracted for 5min with the tank valve closed can mean a big mess........

And........ The tank flush works by shooting a high pressure spray against the tank walls. Having the tank full, negates any effectiveness of the spray head! Just follow the instructions and don't try to reinvent the wheel.

We can always imagine "ifs", but as it pertains to the black tank, I think the "ifs" are very unlikely. If you to not use cement in the connections of the black pipe (ABS), it will still hold water. Not easy to assemble without the cement, so I think it is really unlikely the shoddiest RV builder would assembly without it.

As for the "geyser", I have been there and done that once when I first got my current TC. My TC only has a 12-gallon black tank. It does not take long to fill it with a hose.

I have also overfilled my gray tank. At least two times, all was well, but after being on the road, I saw signs of gray water in the shower pan. Eventually, I found the "P"trap in the shower served as an overflow when I went around a corner. The only solution was to not let it get too full.

Wayne

Believe me (I know from first hand) the water WILL come up and overflow the toilet!!! The seal will keep the solids from coming up, but not the water.

From my personal experience, I now never leave the flush water running unless I'm right there...

So yes, the reason the label is there is for that exact reason.

My procedure is to turn on the flush hose, open the black tank valve, turn on the macerator. The tank will drain faster than the flush hose can put water into the tank so no worries there. When the black tank is empty, I simply open the gray tank and let the gray water run into the empty black tank for about 10 - 15 seconds and then close the gray tank. I will do that two or three more times until the water coming out of the black tank is clear. I then shut the black tank and drain the gray (while the black tank flush hose is putting clean water into the black tank). When gray tank is empty, I turn off the macerator, close the gray tank valve, shut the compartment door and turn off the black tank flush hose.

Hope this helps

Ron

Reddog1 wrote:
I am a bit confused. The black tank has at least one vent. The toilet has a flapper that is sealed. If it were not sealed, waste odor would be in your RV. How could you flood the inside of your RV with black tank waste?

Well, if you keep pushing water into your black tank (through the rinser), and tank fills up...That water you're putting in is going to go somewhere.

If toilet seals hold and it doesnt come out from around the toilet, next place I'd think it would go is up the vent line. If that vent line doesn't have a perfect water-tight seal all the way up...Well, thats one way you could flood the camper.

Or, you might just cause a 'geyser' to shoot out from the vent at the ceiling, kinda like what happened in that one scene in the Robin Williams move, 'RV'? Remember that? :)

Will