Plumbing question overflow and air siphon holes

[joe-ejs]

Hello. I recently setup a 90gl reef ready that I purchased used. The Durso Standpipe (overflow) has about a 1/2" air hole just below water line to stop siphon if required.

The return line back into the tank is a 1" PVC that goes to a 90 elbow and into the tank through loc-line connection, The 90' elbow has a small airhole located on the underside. It makes quite a bit of noise and I am wondering if I really need it since the overflow pipe into the sump has the siphon break hole. Is this hole in the return line a redundant backup in the case the overflow has an issue or is there a different purpose for it?

Thanks

 

[theMeat]

You need a siphon break hole on both lines. They should not be making noise. If the return siphon break is making noise maybe raise the drain to make a return hole go underwater a bit, which is where it should be

 

[RocketEngineer]

I never trust small holes. They clog way too easy. Instead I put my returns right at the surface. I adjust them so they are as high as possible without splashing or noise. Given that there’s always water moving through that opening, it’s not going to clog unless your entire return line gets blocked and that’s pretty noticeable. Simple is best.