Topp B27001SV-3 23" x 31" 3" Side Vent Poly Basin (w/4" Grommet Inlet Drilled)The Side Vent Sump and Sewage Ejector Basins' unique design has been developed for efficient maintenance, reducing service time dramatically. With the vent pipe remaining intact, gone are the days of cutting then repairing the vent pipe for achieving regular pump maintenance. This approach to the design of this basin easily reduces the time for your service calls by one third. 50% more volume than the industry standard 18" x 30" basin. (65 U. S.