How loud simple DDC should be?

[rioja]

Is the system done bleeding yet? A little bit of cavitation in the pump cavity can produce a lot of unwanted noise. Do you have the pump sitting on the case or did you use any isolation method to reduce the amount of vibrations transferred to the case? A little insulation goes a long way in reducing the noise.

here is how pumps sit in the case



i.e. they screwed vertically directly to the case
i have special rubber/gel pad for them, but didn't use it because some ppl worried me about possible overheating.
air mostly went out from loop i guess, system is running a fewhours already. also u may see a little whirlpool in the right res on the pic. there is no much vibration by the touch.

just dont know. i read before that pump ddc is very quiet.
but not in my case, sound is remind some yowl similar to bad chipset cooler at 5000rpm

btw, dont i need any greasing or smth? those white ball (ceramic?) on which impeller rotates, it's greasing only by water?