I have 2 one inch drains. Instead of doing a durso, i did the herbie by cutting one drain pipe about 4 to 5 inches below where the waterline in the overflow would be. The second drain is about the level of where the waterline would be in the overflow towards the top. I then put a gate valve on the short drain pipe and slowly close it till water rises just to the top if the other drain where it slowly goes done the sides if the pipe. This way i get full siphon and alot of water going down the short pipe and very little going down the tall pipe (it acts more of an emergency drain but it stays wet with a little water flowing through it. Hope that helps.Question, How did you convert it to a herbie if it was drilled for a durso?