Drainage Rates
The City of Seattle charges property owners a fee for stormwater management services based on each property's estimated impact on the City's drainage system. These fees are billed as a separate line item on King County property tax statements.
Starting January 1, 2008, the City of Seattle changed the drainage rate structure which underlies the calculation of the drainage fee. The current structure improved equity among customers by more accurately reflecting customers' impacts on the drainage system.
Small residential parcels (single-family homes, townhomes, and duplexes less than 10,000 square feet) are charged a flat rate per parcel based on parcel size. All other parcels, including residential parcels over 10,000 square feet and all commercial and industrial parcels, are charged a per square foot fee based on a parcel’s estimated percent impervious area.
Learn more about who pays a drainage bill, how it is calculated, and where to direct payments.
Small Residential Annual Rates
2025 rates per parcel(1) are effective January 1, 2025.
| Parcel size | 2025 |
|---|---|
| Under 2000 sq. ft. (2) | $235.28 |
| 2000-3499 sq. ft. (2) | $447.08 |
| 3500-4499 sq. ft. | $572.64 |
| 4500-5499 sq. ft. | $672.93 |
| 5500-6499 sq. ft. | $764.98 |
| 6500-9999 sq. ft. | $929.48 |
All Other Properties Annual Rates
2025 rates per 1,000 square feet are effective January 1, 2025.
| Property type | 2025 |
|---|---|
| 0-10% Impervious: | $59.82 |
| 11-20% Impervious: | $65.11 |
| 21-35% Impervious: | $94.46 |
| 36-50% Impervious: | $123.19 |
| 51-65% Impervious: | $138.77 |
| 66-85% Impervious: | $183.25 |
| 86-100% Impervious: | $216.17 |
2024 Small Residential Annual Rates
2024 rates per parcel(1) are effective through December 31, 2024.
| Parcel size | 2024 |
|---|---|
| Under 2000 sq. ft. (2) | $229.93 |
| 2000-2999 sq. ft. (2) | $379.58 |
| 3000-4999 sq. ft. | $524.59 |
| 5000-6999 sq. ft. | $712.36 |
| 7000-6999 sq. ft. | $898.51 |
2024 All Other Properties Annual Rates
2024 rates per 1,000 square feet are effective through December 31, 2024.
| Property type | 2025 |
|---|---|
| Undeveloped (0-15% Impervious): Regular |
$60.44 |
| Undeveloped (0-15% Impervious): Low Impact (3) |
$35.02 |
| Light (16-35% Impervious): Regular |
$89.69 |
| Light (16-35% Impervious): Low Impact (3) |
$69.72 |
| Medium (36-65% Impervious): Regular |
$127.08 |
| Medium (36-65% Impervious): Low Impact (3) |
$102.68 |
| Heavy (66-85% Impervious) | $167.91 |
| Very Heavy (86-100% Impervious)(4) | $200.23 |
(1) Single Family Residential & Duplex parcels less than 10,000 square feet which are charged a flat rate per parcel rather than a fee based on the percent impervious. Rates for other properties are per 1,000 square feet based on the percent of impervious surface.
(2) Beginning in 2016, the under 3,000 sq. ft. tier was split into two tiers to minimize the variance between properties in each group in terms of lot size and percent impervious.
(3) A customer in the Undeveloped, Light or Medium rate category with a significant amount of highly pervious (absorbent) surface may qualify for the Low Impact rate.
(4) "Very heavy" does not necessarily mean heavily developed. A parking lot would be classified as "very heavy" since it is 100% impervious.
Drainage fees do not appear on your utility bill but are collected with your King County property taxes. The fee is shown on your tax bill as SWM (Surface Water Management) or Drainage. You can view your drainage fee by entering your property tax ID in the King County Property Tax Information System.
Eligible low income customers can receive a credit. Learn more about the Payment Assistance Program.
Related links
Understanding Your Drainage Bill
King County Property Tax Information System