Models vary, so take the humidifier with you when choosing the pvc so you can check the fit. If it is slightly loose you can seal a short piece into the spout with silicone. The only problem is you will have to make at least one joint detachable for cleaning the tubing. A tip. Don't make your horizontal pipe perfectly level. If you do some water will just sit in the pipe and stagnate. I've also wrapped rubber (such as bicycle tire inner tube) around the pvc joint at the humidifier spout so I can pull it apart occasionally. Then add fittings (joint collars, angles, etc.) as needed to aim it where you want.