DonW
R.I.P.
Actually that would be under perfect conditions, If you include elbows at all or other restricting fittings it cuts it way down to around 1,500gph. Most of the charts I've seen rates drains at 1,500 gph because of that.
The charts are based on open top pipe which makes them inaccurate since nobody uses open top pipes. A 1.5" herbie will flow 3800gph easily partially closed.
Don