A method of effecting efficient flow equalization in a settling and retention basin having a peripheral wall housing a removable design flow equalization port and a filter member exteriorly of the peripheral wall by (a) observing the height of liquid level induced during wastewater flow upon the filter member relative to the flow equalization port. Thereafter (b) determining whether the observed height of step (a) is outside a desired optimum height range reflective of meeting the design flow characteristics of the design flow port. Thereafter (c) replacing the design flow equalization port with a different size flow equalization port based upon the performance of step (b).