How do you switch between holding tanks.

So connect the water and run the tub and see what fills. Run the kitchen see what fills. If you start with some beer you should be using the toilet by now and see what moves. Bath sink same thing. Any other fixtures? Do the same.

Now drain the tanks using the two levers and see if all is empty.

The OP said the "display panel" shows 2 black and 2 grey tanks. I'm pretty sure that just means the manufacturer used a panel with extra display lights but that the RV only has 1 grey and 1 black tank. My TT panel shows 2 grey tanks but we only have 1.

You'll have a pull handle for each tank. My old unit had three tanks. There were three pulls. I painted the gray ones with silver spray paint so I would know they were gray water. There's nothing like accidentally dumping sewage when you thought you were dumping just sudsy water.

I would go with those saying if you only have one bathroom then one black tank and the panel is most likely generic so somewhere in the line a trailer has 2 black tanks. As you use the trailer just watch and most likely only 2 or the 4 will show anything in the tanks. Usually takes about 3 days to fill the black tank for us.

myredracer wrote:
Aha my little munchkins, but somebody posted the link in the 3rd post down. :W Maybe should have been in bold and a bright color to attract more attention?

Just an observation, it's funny sometimes - it seems sometimes forum members skip past many or all of the already posted thoughts, opinions, facts and links and go straight to posting what's on their minds.

It must be a terrible burden, being perfect as you obviously are.

Aha my little munchkins, but somebody posted the link in the 3rd post down. :W Maybe should have been in bold and a bright color to attract more attention?

OP has not said that the TT in his sig. is not the one he is asking about. Am interested to hear what he finds out.

Just an observation, it's funny sometimes - it seems sometimes forum members skip past many or all of the already posted thoughts, opinions, facts and links and go straight to posting what's on their minds. Kinda like grade school when the teacher asks a question and you're the first to throw your hand way up in the air, lol. Have been known to do it myself even... :S

Sprink-Fitter wrote:

myredracer wrote:
It seems some did not notice the link to the OP's trailer floorplan near the beginning of this thread, so hear it is. It shows one bathroom which would suggest one black tank.

If you assume the trailer in his signature is the one he is asking about, the link is not in his post.

It really doesn't matter what the display panel indicates (besides trying to solve the owner's bewilderment). The tanks are drained through the two exterior connections and no inter-tank connections would have to be dealt with if there are no separate valves for them.

One clue as to tank numbers may be the number of vents coming through the roof. Typically, there will be one vent per tank.

myredracer wrote:
It seems some did not notice the link to the OP's trailer floorplan near the beginning of this thread, so hear it is. It shows one bathroom which would suggest one black tank.

If you assume the trailer in his signature is the one he is asking about, the link is not in his post.

myredracer wrote:
It seems some did not notice the link to the OP's trailer floorplan near the beginning of this thread.

You're right, shame on me.

The bathroom sink is probably plumbed into the black tank, mine is and I like it.

It seems some did not notice the link to the OP's trailer floorplan near the beginning of this thread, so hear it is. It shows one bathroom which would suggest one black tank.