It's definitely a problem with most air-fed ozonators. I suggest people buy the ASO 250 from AquaSun and buy a cheap aquarium pump at Wal mart or someplace similar. Air dryers can be bought from Enaly or from lab supply places like Cole Parmer. This package costs a lot less than a Nature Kleen. I just finally replaced my ASO 250 last night from my hot tub. It had been running 24/7/365 for five years with a commercial air dryer.
Lots of other cheap (especially chinese) ozonators will certainly break down a day after the warranty is up. Sigh!!!!
Happy Canadian Turkey Day Weekend!