I previously had a reef tank but turned it into a high-tech freshwater planted. This has been an issue for 2 years. I have seen soooo many videos showing how to drill holes in the pvc pipe, adding this cap on this or that, making a contraption that makes a U, ect. Nothing really truly made it quiet. I'm telling you this, this worked 100%. I'm going to be nervous that my pump went out because I don't hear anything. Did it take like 45 min to dial it in just perfect? Yes. It's worth every second. All I can hear now is the power head and the occasional ato kicking in. I simply opened the emergency valve 100%, mostly closed main, then slowly opened the main till it was just slightly trickling down the emergency. Plus, not to mention this has another benefit, if the main is stopping up, you will start to hear gurgling sounds again hinting at a cleaning.
So if you have a 600 litre ( water volume ) tank and you need × 5 times the cycle rate ( using Herbie overflow ) ..what is the thickness required in the primary ( Siphoning ) and emergency pvc pipes, so that the Siphon remains as quite as possible without water crashing. Also what type of overflow box ( same as yours ) should i use. I am doing freshwater fish tank with sump. If it's a 5ft tank ..how big ( dimension ) should the sump be?