I have an old Kellog American 120 gallon horizontal compressor that I frankensteined up several years ago. Works real good. I drain it regularly but don't like the rust colored water I am seeing. Although I must admit, I have seen it on every compressor I have ever drained. The "PVC IRON" pipe thread has me rethinking my use of 3/4" PVC there and I will probably go back with iron pipe sometime after the new year. Is there a way I can clean the tank out? Maybe coat the inside like a gas tank to protect it from rust? What's the scoop?