LOUD one 1200

I heard some good things about the quiet one 1200 pump so I picked one up. First thing that I noticed was the 1/2" brass barbs I got didn't go on to easily. Seems like the threads were just slightly to large. I still managed to get them on but it required a bit of force which is not good when using brass and plastic. After I threw it in my system, it immediately starting leaking at the outlet even though I used teflon tape when applying the barbs. So I spent the evening draining the system, got my wrench, reapplied the outlet barb so that it was screwed down further, and gave it a generous silicone bath. After letting that dry out last night, I refilled the system this morning and am now letting it bleed. No more leaks but now it is loud as hell. I am almost sure it is the impeller vibrating against something. It comes and goes randomly, although unfortunately it is present more often than not. It is a rather irratating so it looks like I won't be needing my rheostat much as I might as well run the case fans at full speed to drown out the noise. Maybe I just got a lemon but since it is all I have to go by, this pump gets a thumbs down from me. I don't have the time or patience to drain the system yet again to put in a new pump anytime soon although if I may hang on to my via aqua 1300 I was going to sell for sometime in the future. I like my eheim 1250 alot but wanted something cheaper for this rig, too bad I didn't get a danner

First off I have this pump and had the same problem with the threads feeling too tight. Some swipes with some heavy grit sandpaper on the brass barbs threading fixed that. I then uses a few wraps of thread tape and the barbs went on smoothly and never once leaked.

Mine was also loud at first. Once I cleared all the air out of the system and dampened the vibration its now fairly quiet.
Im sorry to hear yours is giving you problems cause Im happy with mine. Hope you get it figured out.

Is the noise caused by vibrations or the pump itself?

It's the pump itself. I know that some vibration is normal and can be dampened w/ neoprene or foam, etc. This is coming from inside the pump, you can hold it in your hand and is still quite loud.

It does that untill youre done fully bleading, its just the impeller swoosing around the air..

I've seen some pumps that like to hold an air pocket behind the impeller around the magnet assembly. You could try turning it off and tapping it against the case with the outlet facing upward to try and release it.

Since there's actually no bearings in most magdrives, some air trapped back in there would make it quite loud.