overflows

[CalmSeasQuest]

Other people have also made their overflows quiet by placing a zip lock bag in them. But im not familiar with how this works.

IME, There are 2 parts to making an overflow quiet, waterfall and drain(s).

Waterfall - Having the shortest waterfall possible tends to be quieter. Also, having water flow slow enough over the weir that it "adheres" to the backside of the overflow and limits the splashing noise That's where my Ziplock Silence mod comes in handy.

Drain(s) - A drain running full siphon is virtually silent and provides the greatest flow-through. The problem is safety. A drain running at full capacity provides no margin for error. Even a partial blockage or slow down can result in an overflow. It also tends to surge and gurgle as it goes in and out of full siphon based on the amount of water available in the overflow. This is where the Herbie or Bean Animal designs come in by providing a second (or in the case of the Bean, a third) overflow. You "tune" the primary overflow by slightly reducing the capacity of the primary, full siphon drain using a gate valve and allow a small amount of excess to go down the second drain - both of which are silent.