Most overflows sound that way, it is the water "falling" into the hose as it is gravity fed, as long as the level in the sump is correct and the level in the tank is maintained, then you are fine. That sucking sound is totally normal for overflows.
ed. Unless the part of the overflow is in the tank and you are getting air in the "U" tube that is used to siphon, then that could be a huge issue as you could loose siphon and possibly flood the tank. But I think your noise is from the back (drain) side of the overflow. |