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Environmental Services

working for clean rivers

Phone: 503-823-7740

Fax: 503-823-6995

1120 SW 5th Avenue, Suite 1000, Portland, OR 97204

Calculating Sewer Volume

Calculating Sewer Volume

The City of Portland calculates residential single family or multi-family sewer volume using actual water consumption, class average or winter average. 

The city bases sewer volume charges on actual water usage or an average, whichever is lower. 

Actual Water Consumption

The water consumption measured through your water meter. 

Class Average

The average water consumption for a specific account class, such as residential single family or residential multi-family. The city uses class average when there is no water use history or when a winter average is not available. 

Winter Average

The average water consumption for a specified billing cycle in winter and early spring. Most water used indoors during this time of year enters the sewer system. Since much of the water used in warmer months waters lawns and gardens and doesn’t enter the sewer system, the city uses the winter average as the most equitable way of determining sewer volume. 

The city applies winter average volume to residential accounts during billing periods outside the winter average review period. During those billing periods, the city bills customers the winter average consumption or actual water consumption, whichever is less.

Winter Average Review Periods

Monthly billing cycles

December 1 – April 30 

Bi-monthly billing cycles

January 1 – April 30 

For residential accounts billed quarterly, the city calculates the winter average on water readings taken between February 1 and April 30.

How to Calculate Your Winter Average

Quarterly Accounts 

Divide the total winter average review period consumption by the total actual days of service in your review period (days between the billed meter readings in the winter average review period) and multiply by 90. 

Bi-monthly Accounts 

Divide the total winter average review period consumption by the total actual days of service in your review period (days between the billed meter readings in the winter average review period) and multiply by 60. 

Monthly and Budget Billing Accounts

Divide the total winter average review period consumption by the total actual days of service in your review period (days between the billed meter readings in the winter average review period) and multiply by 30.

Winter Average Example

Date                 Reading           Consumption      Days between readings

09/17/03            1026                65ccf*                          92

12/16/03            1052                26ccf                            90

03/19/04            1095                43ccf                            94

06/17/04            1144                49ccf                            90

43ccf ÷ 94 days x 90 days = 41ccf

*one ccf equals 100 cubic feet of water

Minimum Use Average

Accounts billed for 0 to 2 ccf during the winter average billing period will be assigned the following winter average based on billing frequency: 

Monthly Billed Account

Metered winter average water use of 0 ccf will be assigned 2 ccf minimum use average per billing period.

Bi-monthly Billed Accounts

Metered winter average water use of 0 to 1 ccf will be assigned 5 ccf minimum use average per billing period.

Quarterly Billed Accounts

Metered winter average water use of 0 to 2 ccf will be assigned 7 ccf minimum use average per billing period. Multi-family quarterly billed accounts will be assigned 5 ccf minimum use average per dwelling unit billing period.

 

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