Fiberglass Tank Approximate 8,000 Gallons, inlet 2 in. on top of tank, manway 32 in. Diameter, (2) Inlets on side of tank at 1 in. and 2-½ in., one on bottom side of tank 2 in. one outlet on bottom of tank on side 3-½ in. Inside measurements: 120 in. diameter. 172 in. H. Overall measurements 120 in. Diameter, 187 in. H.