getting loud gurgle out of your overflow!

[mark]

Trigs, try a elbow pointing down in your overflow box. Cap the pipe above the tee on the outside, then starting with a small drill slowly go larger until the level in the overflow becomes steady and the drain quiets down (can also use a air valve). Once tuned, the air your pulling through the drain is at a minumun, you'll still get some gurgling but that's the nature of this type of standpipe.

For zero gurgling all I know of is the Herbie style but to be safe, they require two holes for drains.