in wall drain pipe repair

[Welbourne]

I know what I need to to, to lower the drain out from a bathroom sink but I do not know how to put a new T in the existing pipe in the wall.
I am replacing a regular sink with a laundry tub in the 1/2 bath in the garage and the drainout is higher than I can use for the laundry tub drain.
I am working with PVC pipe, I assume, as the house was built in the 80's.

[Redwood]

What you have to do depends on what is hidden in the walls.

You can neither assume PVC or, what you have for a configuration in the wall until you open it up.

Can you see white plastic pipe inside the wall>

With the existing trap removed can you feel the turn of the pipe or see it inside the wall? Does it turn left or, right, or go vertical?

[Welbourne]

drain pipe repair

Thanks for the responce. The drainout now is high on the wall and I can see that the vent pipe goes down. I am pretty sure it is PVC but understand I need to cut wall and make sure.