I have the picture here and have read other posts. It seems to me that the only way to prevent freezing of the water in the vent is to have the drain pipe buried at or below the typical freeze line (which I am guessing to be a foot in Oklahoma) with the vent "teed" off at that level in the soil otherwise the water would freeze at that joint (just above the running water) and cause a continual flow. Someone correct me if I am thinking of this wrong.

Craig