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Sewer Service Charge
As part of the annual property tax bill, property owners pay a sewer service charge. This funds the sanitary sewer collection system running beneath our city, as well as the wastewater treatment plant that processes everything that goes down the drain. This charge is calculated directly from the volume of fresh water used by each parcel and the estimated intensity of the resulting wastewater. A per-dwelling unit fee also applies to residential properties, while the usage-based fee is significantly lower. The tabs below display the latest rates, information on how to calculate your total sewer charge, and additional documentation.
Latest News
On July 20, 2023, City Council approved the sewer rate increases for FY 23/24 through FY 27/28 following two public hearings as required by Proposition 218. In addition, notices were mailed out to every property owner of record in April 2023 containing all the rate information below.
Past News
Because of recent changes to the Sewer Service Charge rate structure, residential customers might see a significant change on their bill this year. The charge used to be calculated strictly based on water use, which is how all commercial customers are charged. For Fiscal Year 2018-19, the usage based rate was reduced but a new fixed per-dwelling unit fee has been added. See the tables below for details.
These changes were approved by City Council on March 5, 2018 following two public hearings as required by Proposition 218. In addition, notices were mailed out to every property owner of record in January 2018 containing all the rate information below.
This change was made to ensure reliable revenue as we begin construction on the new wastewater treatment plant and continue work on sewer infrastructure throughout our city. Previously, droughts caused swings in water use, which led to unstable sewer charge revenue just as these major capital projects started. This shift for residential customers aligns the City Sewer Service Charge with many agencies around the Bay Area in both structure and price for the customer.
Please also note that the City Sewer Service Charge matches the cost of providing sewer service, whereas Proposition 13 (1978) caps the increase of assessed property values to two percent per year. This means that your sewer charge can increase more quickly than your base property tax bill. If you have owned your home for many years, the sewer charge could make up a large portion of your total tax due to the County of San Mateo.
Sewer rates have been approved for 2023-24 as follows:
| Residential Class | Rate |
| Class A usage-based fee | $12.15/CCF |
| Per-dwelling unit fee | $61.94/mo |
| Commercial Class | Rate |
| Class B | $24.31/CCF |
| Class C | $31.93/CCF |
| Class D | $43.30/CCF |
| Class E | Case-by-Case Basis |
| Minimum Charge | $61.94/mo |
Sewer Rates have also been approved through Fiscal Year 2027-28. Please see the Proposition 218 Notice (PDF) to see the sewer rates for upcoming years.
To learn more about the different user classes, view the Sewer Charge Administrative Regulations (PDF).
Residential: The sewer service charge for residential customers is based on a fixed monthly fee, plus a usage-based fee.
- Fixed fee: a monthly base charge applies to each dwelling unit on a property. For example, a single family home would be subject to one (1) dwelling unit fee, while a property containing a duplex would be subject to two (2) dwelling unit fees. Apartments, bachelor and efficiency units, and accessory dwelling units are all considered to be separate dwelling units.
- Usage-based fee: the fee based on water use is calculated by multiplying the estimated annual water use by the Class A (residential user) rate per CCF (100 cubic feet). More details on that calculation can be found in the "Calculating Your Usage-Based Fee" section below.
(12 Months x Fixed Fee) + ((Average Monthly Water Use x 12 Months) x Class A Rate)
Commercial: The sewer service charge for commercial customers is based only on a usage-based fee that is calculated by multiplying the estimated annual water use by the commercial rate, based on your user class. For more information on determining your user class, view the Sewer Charge Administrative Regulations (PDF).
(Average Monthly Water Use x 12 Months) x Rate based on user class
Calculating Your Usage-Based Fee
The usage fee is based on water consumption for the five preceding winter months (November through March). These months are used to minimize the impact of irrigation water during warm months, which does not flow into the sanitary sewer system. Your sewer fee can be determined by multiplying the rate for your customer class (see "Sewer Rates" tab) by your average annual winter water usage as illustrated below.
| Water usage in CCFs for Sample Calculation | |||||
| November 2022 | December 2022 | January 2023 | February 2023 | March 2023 | TOTAL |
| 9 | 7 | 6 | 6 | 7 | 35 CCF |
1. To calculate the average water use, take the TOTAL and divide it by 5.
EXAMPLE: 35/5 = 7.0 CCF/month
NOTE: If the usage for any month is zero, the average shall be computed by using the remaining months’ usage that do show water usage.
2. Estimated annual use is calculated by multiplying the monthly average by 12.
EXAMPLE: 7.0 CCF/month x 12 = 84 CCF
3. This annual usage is multiplied by a rate associated with the cost of processing the property’s wastewater. All residential customers are Class A, and commercial customers are assigned either Class B, C, or D. To determine your classification, view the Sewer Charge Administrative Regulations (PDF).
Once you have determined your estimated water use and classification, you are able to calculate the total sewer charge for the fiscal year.
- If you are a residential customer, you are Class A and your usage-based rate is $12.15/CCF. You would calculate your bill as follows:
($12.15 x annual usage of 84 CCF) + ($61.94 fixed fee x 12 months) = $1,763.88 - If you are a restaurant customer, you are Class D and your rate is $43.30/CCF:
($43.30 x annual usage of 84 CCF) = $3,637.20
For full details on the City Sewer Service Charge, please view the Sewer Charge Administrative Regulations (PDF). This document will help you answer questions like:
- What is considered a "dwelling unit" for the purposes of the residential fixed fee? (page 1)
- What determines my user class? (pages 2-3)
- What minimum sewer charges apply? (page 5)
- When and how can I apply for a sewer charge adjustment? (pages 5-6)
The regulations elaborate on San Mateo Municipal Code, Chapter 3.54. The text of this ordinance can also be found in the Administrative Regulations PDF.
For more information on the sanitary sewer system and the important work funded by your sewer charge, please view the brochure on the Wastewater Collection and Treatment System (PDF).
To see the approved sewer rates through Fiscal Year 2027-28, please see the Proposition 218 Notice (PDF) sent out in 2023.