First tank setup - whistling from the drain.

[EricL.]

Hey everybody,

allow me to introduce myself:

My name is Eric, 26 years of age, living in Germany.

I bought a used Aqua Medic Armatus 250 which uses their “Easy Drain”-System. The gurgling sound went away once i adjusted the water level, but what remains is a high-pitch whistle which seems to come directly from the drain pipe. However, i don‘t understand how the pipe should whistle now because the inlet is completely submerged in water, as is the outlet. I noticed some air bubbles coming out of the outlet, though.
I am confused!
It seems like it is sucking in air somewhere... any ideas how to localise and stop it?

See a picture of the plumbing attached. The brown wrap closes a small hole, however, this hole is not the reason for the whistle as i already removed the wrap and closed it tightly, but the whistle sound remained.

Thanks in advance for your help,

Eric

 

[lapin]

It is either leaking/ sucking air or on startup it does not purge all the air out of the pipe

 

[EricL.]

I eliminated the whistle!
What I did was cutting the drain pipe a good amount shorter, it seems like @lapin was right, the pipe was so deep in the sump that it could not purge out all of the air.
The tank is really quiet now, thank you!