For the wash machine:
Pool supply stores, flexible PVC pipe. Can be "glued" with connectors and straight pipe.
For dryers:
8A in Santiago.
Don't use the lined A/C air duct stuff... rodents like to eat the lining!
Just go for the aluminum flexible material.
Dryer outlet pipes should be held a short as possible. If the outlet is upwards (thru the roof)... try to build a siphon service box, so lint which comes back down doesn't get stuck at the machine (causing fire hazard or poor drying) but falls back into a box which can be emptied periodically (easy access).
There are PVC bows available... they are recommended, even with the flexible aluminum pipe material, as the uneven surface causes turbulence which can have some "funny" effects. The plastic 90deg. bows are of a flat surface.
... J-D.