return pipe size on a 120 gallon

[Royal_pudding]

Hi all
I am absolutely hopeless when it comes to plumbing. I have spent hours trying to figure this out and really dont want to jump into anyting since this is pretty permanent.
I am trying to set up a herbie style overflow on a 120 gallon dt, with a 27 gallon custom sump. Sump is located under the tank.
I have a jebao mdc 8000 rated up to 2100gph but am not intending to run it at nearly that flow rate. The Reefmat 500 is probably going to be the limiting factor flow wise, it is rated up to 1500gph.
So, I have to decide on plumbing sizes and that is where I need some help, I need to decide on which size holes to drill.
I was thinking
32mm main drain - 25mm safety drain - 25 mm return line.
Is that reasonable given the equipment I have?
Also, to keep the peace in the household, this thing really needs to be as quiet as can be.

Here's to hoping a kind hearted soul can help a brother out.

 

[DCR]

Those are reasonable drain and return line sizes for a 120 gal. If you are doing a Herbie style system (which will be quiet), I would switch the main drain (or siphon) to 25 mm and make the safety drain 32 mm. I am assuming those are pipe sizes and not hole sizes. They should comfortably flow about 500-600 gph which is fine for a 120 gal