I'm replacing a gas dryer in a condo that previously had 2 plastic flex pipes and a 5ft aluminum rigid duct.
I planned to replace it with rigid steel. I got most of it dry-fitted correctly, except the end of the run. There's about 2 feet between my new run and the exterior vent. See side-view image below (note: the picture does not show that the exterior vent is a little lower and also to the right):
The end of the run is in a tight area, in a small 3x3 closet that also contains a circuit breaker. To get through here with rigid steel ducts, I'll need several elbows and short extenders. I'd rather use a bit of semi-rigid flex vent in a small C-shape instead, for ease of installation and less seams.
The red dashed line in my picture represents where the flex duct would go. It would be about 2 to 2.5 feet long.
Is it OK to use flex duct near the end of a run at this length (about 18 ft total)?
(More generally) If a duct is going to require several quick bends and seams in a tight area, is it ever better to use a single flexible duct instead? If yes, how should that determination be made?
Edit: I ended up admitting to myself that I was trying to be lazy and fanangled a few adjustable elbows to cover this gap. I'd still like to know the answer to #2.