Triple Weave - Is it possible to weave triple width fabric on a countermarch loom?

Sure you can….Thread 1,3,5,2,4,6

Top layer is on 1 and 2

Middle layer is on 3 and 4

Bottom layer is on 5 and 6

You will be weaving one pick on top, then a pick of middle, then a pick of bottom. They you have to come back up starting with the other pick of the bottom, then the other pick of the middle and then the other pick of the top….then back down top, middle, bottom…that is how you have to think while you are treadling. Follow that path in your head.

Your tie-up would be

Treadle 1: tie-up lower lamm to 1

Treadle 2: tie-up lower lamm to 3

Treadle 3: tie-up lower lamm to 5

Treadle 4: tie-up lower lamm to 12346

Treadle 5: tie-up lower lamm to 12456

Treadle 6: tie-up lower lamm to 23456

When you look at that tie-up Treadle 1 and 6 are the 2 picks of your top layer

Treadles 2 and 5 are the 2 picks of your middle layer and

Treadles 3 and 4 are the 2 picks of your bottom layer.

I have attached a quick sketch of the draft.

Hope this helps.