Hi Hope this helps ?? Coped from the WWW
I've had this response from TMC:
"Firstly, thank you for purchasing a Signature Aquarium set. I hear from Helen that you are having issues with noise from drain from your tank?
Due to the setup of the aquarium there will always be some water noise but there are a few things that you can do that may help.
First of all, is ensure that you are delivering approx 580 litres per hour of flow to the tank at the height of the drain. The recommended pump is a V2 PowerPump 1500. If you are using a different pump to this, it may be putting just a little bit too much water down the drain, causing slurping as the air is sucked down as the pipe creates a siphon. If using a V2 PowerPump 1500, use the flow adjuster to click back 2 clicks when clean. On my setup I found this the perfect level of flow in/out of the tank.
The second thing is to discharge the water from the drain pipe a few inches under water in the first chamber of the sump. Mine goes into a filter sock but I don’t think this will make much difference. Doing so may cause the same air pressure issues that we get when applying too much flow. This will mean the pipe may still want to suck air. To alleviate this, pierce a 6-8mm hole in the drain pipe, approx 6 inches above the water level, hole facing outwards over the sump. Ensure all piping travels smoothly too. I did the above on my own Signature aquarium and actually managed to get a very quiet running system.
Simply, these few fixes should get you working a bit quieter. As the system beds in and the pipes grow bacteria, the system will naturally quieten down a bit anyway. However as with most sumped system you will never have it 100% silent due to pumping water up and dropping it back down again!
I hope this of use to you and may I wish you all the best for your future aquarium success."
I'm going to try the hole in the pipe idea