to the external drain system 0055 fig1 a is a simplified schematic representation of the left hand half of the symmetrical configuration of fig1 which is coaxial about a central axis c c u2032 showing again the relation of sealant 20 urine 18 and a sealant flow path 22 in the urine in the entry compartment it is evident that in this configuration due to the vertical orientation of baffle 16 a flow path 22 is predominantly vertical that is downward in the outer compartment as shown and upward in the inner chamber with only relatively small horizontal components around the bottom of baffle 16 a and around the top of stand tube 14 a flow path 22 having sealant 20 overhead is the only portion of the total flow path where sealant recovery can occur thus a corresponding parameter can be estimated as indicated by dimension x representing the effective sealant recovery horizontal flow path length in a typical odor trap of the category of fig1 and 1a with main liquid container 14 having an inside radius r of 5 4 cm and the baffle 16 a having an outside radius of 4 cm the horizontal recovery dimension x is about 0 8 cm from which is obtained the unitless ratio x r 14 8 which characterizes this particular internal structure component x labelled in the figures is an approximate average of the horizontal vector components x of the wastewater flow extending from the middle of the entry opening e g the point of average entry of the wastewater into the sealant to a furthest point along the flow path e g around the baffle in which sealant recovery can occur although the invention contemplates a value x based on the approximate average preferably generally all.