Septic pumping in Spokane County, Washington costs $400-$750 (avg $550). A new septic system installation costs $8,000-$16,050. USDA soil data rates 0.6% of county soils as suitable for septic absorption fields. Approximately 12,944 homes in this county use septic systems.
Septic System Costs in Spokane County
| Service | Low | Average | High |
|---|---|---|---|
| Pumping / Cleaning | $400 | $550 | $750 |
| Routine Inspection | $300 | $450 | $650 |
| Real Estate Inspection | $550 | $800 | $1100 |
| Minor Repair | $1,000 | $1,450 | $7,000 |
| Conventional Installation | $8,000 | $11,450 | $16,050 |
| Aerobic System Installation | $15,000 | $21,450 | $30,050 |
| Drainfield Replacement | $8,000 | $11,450 | $16,050 |
| Perc Test | $1,200 | $1,700 | $2,400 |
Cost estimates based on regional market data for Spokane County, Washington. Actual costs depend on system type, site conditions, and provider.
Soil & Septic Suitability in Spokane County
Drainage Class
Well drained
Hydrologic Group
C
Unique Soil Types
138
Avg Bedrock Depth
2.8 ft
Dominant Soil Types
| Soil Series | Coverage | Drainage | Hydro Group |
|---|---|---|---|
| Marble | 669 | Well drained | A |
| Phoebe | 638 | Well drained | A |
| Ardenvoir | 608 | Well drained | B |
| Seaboldt | 580 | Well drained | C |
| Battleplain | 565 | Somewhat excessively drained | A |
Septic Tank Absorption Field Suitability
USDA NRCS rates soil suitability for septic absorption fields across this county:
Overall rating: Very limited
Groundwater & Water Table in Spokane County
Monitoring Wells
1
Avg Depth to Water
98.2 ft
Median Depth
99.2 ft
Shallowest Recorded
86.7 ft
Water table depths in this county are generally favorable for conventional septic systems.
Source: USGS National Water Information System. Based on 62 measurements from monitoring wells.
Septic Regulations & Permits in Spokane County
State Regulatory Body
Washington State Department of Health
Inspection Required for Home Sale
Yes
Nitrogen Reduction Areas
Yes
Advanced Treatment Required
In designated areas
Mandatory time-of-sale inspection since 2008.
Contact the Spokane County health department for current permit requirements, fees, and approved system types.
Septic System FAQ for Spokane County
How much does septic pumping cost in Spokane County?
Septic pumping in Spokane County, Washington typically costs between $400 and $750, with an average of $550. Costs vary by tank size (1,000-1,500 gallons is typical), ease of access, distance from the pumping company, and how full the tank is. Most homeowners should pump their tank every 3-5 years.
How much does a new septic system cost in Spokane County?
A conventional septic system installation in Spokane County typically costs $8,000-$16,050. An aerobic treatment unit (ATU) costs $15,000-$30,050. Given the predominantly well drained soils in this area, some sites may require alternative system types. Costs include the tank, drainfield, permits, and labor.
Do I need a permit for a septic system in Spokane County?
Yes. Virtually all counties in Washington require a permit before installing, repairing, or replacing a septic system. The permit process typically involves a soil evaluation or percolation test, system design by a licensed professional, application to the county health department, and one or more inspections during installation. Contact the Spokane County health department for current requirements and fees.
What soil types are in Spokane County and how do they affect septic systems?
Spokane County has predominantly Marble, Phoebe, Ardenvoir soils. The dominant drainage class is Well drained with hydrologic group C. The USDA rates 0.6% of surveyed soils as "Not Limited" for septic absorption fields, 3.9% as "Somewhat Limited", and 95.5% as "Very Limited".
Is a septic inspection required when selling a home in Spokane County?
Yes. Washington requires a septic system inspection as part of the property transfer process. This typically involves a certified inspector evaluating the tank, drainfield, and all system components. The inspection cost in this area averages $800. If the system fails inspection, repairs or replacement may be required before the sale can proceed.
How often should I pump my septic tank in Spokane County?
The EPA recommends pumping your septic tank every 3-5 years for a typical household. The exact frequency depends on tank size, household size, and water usage. A 1,000-gallon tank serving a family of 4 should generally be pumped every 3 years. With approximately 12,944 septic systems in Spokane County, there are many local providers offering regular pumping services.
Can I install a conventional septic system in Spokane County?
It depends on your specific site. USDA soil data shows that 95.5% of soils in Spokane County are rated "Very Limited" for septic absorption fields, while only 0.6% are "Not Limited." This means many properties will require alternative systems such as mound systems, pressure distribution systems, or aerobic treatment units. A percolation test ($1200-$2400) and soil evaluation are required before the county will approve a system design.
How long does a septic system last in Spokane County?
A well-maintained septic system in Spokane County typically lasts 25-30 years, though some components may need attention sooner. The concrete septic tank itself can last 40+ years, while the drainfield — the most critical and expensive component — usually lasts 15-25 years depending on soil conditions (Spokane County has predominantly well drained soils). Regular pumping every 3-5 years and avoiding excess water usage are the two most effective ways to extend system life.
Data last updated: 2026-04-13