Can I cut up ductwork to go around an obstruction

[asterix2112]

Question, I have a normal 8 1/2" x 3 1/2" (approx) duct running down between 16" spaced joists 7 1/4" high. It's running to the small bathroom heating vent and is the end of the line. Trouble is a new bath, replacing a shower is going in and the drain, overflow and p-trap all need to go into that space. Question is, can I cut the duct on either side of the drain piping and hand make some sheet metal ducts, or some flexible ducting that will go around the piping, attaching back to the 8"x3" duct on each side (making sure it is sealed good), ensuring that overall air flow volume is about the same? I can not see what not (though it will be a pain to do!), but thought I'd get some feedback.

Thanks in advance,

- John

[Ed Imeduc]

That 8 1/2"X 3 1/2" just dont sound right but could be. most of the time small wall stacks like that are 3 1/4"X 10"That you would work off a 6" round pipe Id try and cut out the 8X3 where you need the plumping tobe then reshape the duct to round and work a 5 " round pipe from one to the other.Dont use duct tape use the aluminum kind to patch it up .

ED ;)