said by XXXXXXXXXXX1:My Quietside has PVC piping for intake and exhaust venting. I attached a pic. It's been a great unit thus far!
Intake doesn't matter, you could even run the black stuff without any issues. For exhaust, I'd run the first 5' in CPVC. Water heaters and boilers have hotter flue gases than your typical Cat-IV forced air furnace. The PVC product that I've dealt with is rated up to 149, the CPVC product was rated to 190. If the flue gas temperatures exceed the rating, it causes too much expansion/contraction and it may eventually separate the joints, which causes flue gas spillage into occupied space. If you run CPVC for the first 5' of the exhaust, the flue gases cool down enough by the time they reach the PVC run that they're within specs for the material.
By the way guys, if you see your condensing appliances vented with the black stuff, get it changed out ASAP.. It's not rated for hot flue gases, the cement is weak and joints separate almost by looking at'em.