Can dryer vent touch ABS pipe

If you have it too long with too many bends you will be creating a fire hazzard. You need to be able to clean out that dryer vent. If you have it running 15' one way and 10' another with 90 degree turns, then you might run into fire safty issues. If you can put it up against an outside wall, make your hole there on the second story. This will save you money, reduce fire risk greatly, and you wont have to pay a small fortune to have someone run a 30' snake to clean it every year.

This is not likely to be a major problem, but I can think of two ways it might cause trouble. One is noise, which can occur when the pipe moves due to thermal expansion or rapid water shutoff. Another is galvanic corrosion, which can occur when non-copper metals contact copper water pipes.

Either of these issues can be easily addressed by placing a section of foam pipe insulation around the copper pipe in a way that prevents contact with the duct.