How to Calculate Your Sewer Bill

Who's your sewer provider?
Charleston Water System provides billing services for other sewer utilities within our water service area. Your sewer provider is listed on your bill. If Charleston Water is not your sewer provider, visit your sewer utility's web site for rate information, or call us at 843-727-6800. List of other sewer providers

The information below applies to Charleston Water System sewer customers only. 

Sewer rates
Learn more about our rate structure and view current and past rate schedules here.

About your sewer bill

Your Charleston Water System sewer bill is based on your water use. This is because most water ends up flowing into the sewer system. 

Your sewer bill includes the following charges:

         Minimum Bill + Volume Charge = Sewer Bill

All customers pay the minimum bill, which includes up to 2 Ccf (1,496 gallons) of sewer use. If you use more than 2 Ccf, you'll pay an additional volume charge. To calculate your sewer bill, you need to know the following:

  • How much water you used
    This is listed on your bill. Sewer customers that do not have metered water service are billed the non-metered flat rate, which is $56.05 for inside-City customers and $77.37 for outside-City customers (based on 6 Ccf of sewer volume).

  • Whether you live inside or outside the City of Charleston
    This affects your minimum bill and volume charge.

Here's how to calculate your sewer bill:

  1. Determine your billable sewer consumption
    For single-family residential customers that don't have a separate irrigation meter, your billable sewer use is 95% of your water consumption (multiply your water consumption by 0.95). All other customer classes are billed for sewer based on 100% of water use (meaning your billable sewer consumption is the same as your water consumption).

    A residential customer that used 6 Ccf of water and does not have a separate irrigation meter:

            6 Ccf x 0.95 = 5.7 Ccf billable sewer

    A residential customer that has a separate irrigation meter and used 8 Ccf of water:

             8 Ccf billable sewer

  2. Determine your minimum bill
    If your billable sewer consumption is between 0 and 2 Ccf, this is your total sewer bill. If you used more than 2 Ccf, continue to step 3. 

       Minimum Bill Amount
       Inside City:      $29.00
       Outside City:  $41.00 
      Rates effective 1/1/2016

  3. Determine how much sewer you used above the 2 Ccf minimum
    For example, if your billable sewer consumption is 5.7 Ccf, the first 2 Ccf are included in your minimum bill. That means you'll pay a volume charge for the additional 3.7 Ccf.

             5.7 Ccf (total use)  -  2 Ccf (minimum bill) = 3.7 Ccf
  4. Calculate the volume charge
    Find the appropriate unit rate based on whether you live inside or outside the City of Charleston, and multiply it by the amount of water you calculated in step 2. 

     Sewer Use (Ccf)
     Inside City Rate  Outside City Rate
     Over 2 Ccf $7.31 per Ccf   $9.83 per Ccf
    Rates effective 1/1/2016

    Continuing the example above, if the residential customer lives inside City of Charleston, she would calculate her volume charge like this:

            3.7 Ccf  x  $7.31 = $27.05 (volume charge)

  5. Add the volume charge to the minimum bill
    This is your total sewer bill.
           $29.00 (minimum bill) + $27.05 (volume charge) = $56.05

    Note: Residential customers that don't have a separate irrigation meter will not be charged more than the maximum sewer charge, which is based on 17.1 Ccf of billable sewer use.

    Maximum Sewer Charge
    For residential customers without an irrigation meter
    Inside City:     $139.38
    Outside City:  $189.43 
    Rates effective 1/1/2016