Hi,
Can't find much info out there, but I'm intrigued.. I havn't come across a weir setup such as that.. It sounds like you're supposed to adjust the drain tap so the level of the water in the weir is just below the top of the overflow pipe, and if the overflow pipe top is level with the weir top (top of combs or just beneath), this would potentially give you a silent way of getting water to the sump, (of course until it goes crashing into the sump), but that's a sump noise prob!
I am right in thinking the drain is near the bottom of the weir and the overflow level with the top?
I'm keen to see if you can actually adjust the drain tap to give a near silent cm or so drop over the weir, of course if debris gathers within the drain tap then the flow is going to change thereby needing re-adjustment.
Let us know how it goes..
p.s. Well done for buying the pre-drilled tank etc!, I'm sure the extra money is well worth it
(speaking from personal diy experience!
) oh, yeh, I'd use a slotted horizontal return pipe sunken into the sump (slots facing upwards), and foam on the top to minimize bubble noise and splashing.