Which tank is this? Question, when you go take a look at your dump valves, Is one larger than the other (3 inch and an inch and a half) If so it's the big one.. That simple.
Suggesiton, put a clear extension or elbow in the line (I use one of each coming off the rig to the hose) You open one valve it flows brown, the other much lighter in color.. The black tank is the darker one.
Second: I have a "Tornado" and I'm half pleased with it.. It does out perform the original equipment "Flusher" which is something of a bad joke in my book.
However I still do not get clean sensors (placement is poor)
I find a Valterra Master Blaster "Work alike" which I made myself out of half inch PVC shoved down the toilet works great with a bit of skill on my part
I suspect the wand called "The RV Swivel Stick" by Camco would do so too
This wand comes in two types. .One has a flexible section (Which I'd need) and others do not.. My toilet is 'Offset" (The pipe runs at an angle)
I normally use the Tornado for day to day.. Use the wand when I really need clean sensors.
I've had bunch of folks "Guarantee" that this or that black tank product would keep my sensors working properly...... Right.. Sure.. Not one has yet.
Only the blaster wand has worked,, have not tried the "Swivel Stick" yet
Camco 40094 RV Swivel Stik Holding Tank Rinser with Shutoff Valve
While googling for that I found a few forum posts (Assorted forums) all saying it worked. Just so you know... I know my home made master blaster works too.