There are a couple major factors in sump moise
Water flowing out of the tank via the overflow
Water entering the sump
Velocity of water flowing thru the sustem, faster creates more noise potential
In
sump skimmer , pump vibration , intake noise from venturi/beckett injector, etc
return pump vibration, over all system size factors in as well
How each of these points is adressed will determine the noise level, but a well designed sump shouldn't make a lot of noise
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