A PRIMER ON MEASURING SEWAGE FLOW

There are several types of yardstick used to measure sewer effluent.  The use of one or another depends on the context in which a measurement is needed.

MGD = million gallons per day.  This measure is used for large quantities of effluent, as in the contract between Scio and Ann Arbor, and reflects a daily amount of sewage that passes through the transit pipelines. 

CCF = One hundred cubic feet.  This is the measure used for quantifying sewer use for billing purposes, whether in a household or a business.  This measure is not tied to a specific time frame; it reflects the cumulative quantity of sewage over the designated time – a day, a month or a quarter.  The typical home uses about 21.5 CCF per month.  There are 748 gallons in one hundred cubic feet.

REU = Residential equivalent unit.  This measure is used to estimate the number of home or commercial connections to the sewer system that the sewer capacity allows.  Any new construction, whether a home or a business, must have an estimated flow value for its sewer usage, as required by the MDEQ and the Township.  This helps the Township keep track of the growth of gallons coming into the system for each new building.  One REU has a value of 300 gallons per day. 

A new residence will subtract one REU from the total number of REUs remaining in the system.  There are design tables for estimating the number of REUs that a commercial build will require; the table considers many different factors including building size and uses.  Whenever a new building comes into the existing sewer system, there is a tapping fee – the charge for making a new connection to the system.  The fee is based on the number of REUs required by the building.

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Last modified: 06/26/11