You guessed it, I used PVC!
But only where it's covered from fragging somebody, to save money. Like in the ceilings. Where it's out in the garage, I used the rapidair stuff.
Things to consider when running your lines;
Use a braided flex-hose to connect the compressor to the mounted hardlines to eliminate vibration damage to the mounted lines.
Always run them up-hill instead of level, that way condensation will fall back to the previous segment. Kinda like drip loops. I put T fitting's before segment changes with a foot of down pipe and fittings on their bottoms to drain the line condensation occasionally.
If you're going to put an outside fitting on the back wall or something make sure there's a couple feet of line from the main in cold climate like I live in, and have a valve on each end of that before going out the wall. Make sure you go uphill to the 'out' line too. I learned the hard way when the cold outside air caused condensate freezing in my hardlines. Double valves and another filter closer to the compressor helped that prob.
Hope those are helpful.