Hello, I’m still quite new on the subject of compressor. I have a small compressor of Einhell for occasional impact screwing, blowing away dirt etc. which has now been under pressure for 4 weeks and I drained it yesterday down on the tap. Of course, brown/rusty water came out. How often do you have to drain the boiler and how do you maintain it from the inside? You could inject rust protection oil through the tap from time to time. Thank you for your remarks Greeting Gale