Septic pumping in Washington County, Missouri costs $250-$500 (avg $350). A new septic system installation costs $4,750-$9,500. USDA soil data rates 0% of county soils as suitable for septic absorption fields. Approximately 2,822 homes in this county use septic systems.
Septic System Costs in Washington County
| Service | Low | Average | High |
|---|---|---|---|
| Pumping / Cleaning | $250 | $350 | $500 |
| Routine Inspection | $200 | $250 | $350 |
| Real Estate Inspection | $300 | $450 | $650 |
| Minor Repair | $600 | $850 | $4,200 |
| Conventional Installation | $4,750 | $6,800 | $9,500 |
| Aerobic System Installation | $8,900 | $12,750 | $17,850 |
| Drainfield Replacement | $4,750 | $6,800 | $9,500 |
| Perc Test | $700 | $1,000 | $1,400 |
Cost estimates based on regional market data for Washington County, Missouri. Actual costs depend on system type, site conditions, and provider.
Soil & Septic Suitability in Washington County
Drainage Class
Well drained
Hydrologic Group
D
Unique Soil Types
72
Avg Bedrock Depth
2.4 ft
Dominant Soil Types
| Soil Series | Coverage | Drainage | Hydro Group |
|---|---|---|---|
| Sonsac | 335 | Well drained | D |
| Lily | 320 | Well drained | B |
| Goss | 307 | Well drained | D |
| Higdon | 303 | Somewhat poorly drained | C/D |
| Rueter | 288 | 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 Washington County
Monitoring Wells
1
Avg Depth to Water
205.9 ft
Median Depth
206.7 ft
Shallowest Recorded
194.8 ft
Water table depths in this county are generally favorable for conventional septic systems.
Source: USGS National Water Information System. Based on 20 measurements from monitoring wells.
Septic Regulations & Permits in Washington County
State Regulatory Body
Missouri Department of Health/Environment
Inspection Required for Home Sale
No / Varies
Nitrogen Reduction Areas
No
Advanced Treatment Required
No
Contact county health department for specific requirements.
Contact the Washington County health department for current permit requirements, fees, and approved system types.
Septic System FAQ for Washington County
How much does septic pumping cost in Washington County?
Septic pumping in Washington County, Missouri typically costs between $250 and $500, with an average of $350. 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 Washington County?
A conventional septic system installation in Washington County typically costs $4,750-$9,500. An aerobic treatment unit (ATU) costs $8,900-$17,850. 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 Washington County?
Yes. Virtually all counties in Missouri 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 Washington County health department for current requirements and fees.
What soil types are in Washington County and how do they affect septic systems?
Washington County has predominantly Sonsac, Lily, Goss soils. The dominant drainage class is Well drained with hydrologic group D. The USDA rates 0% of surveyed soils as "Not Limited" for septic absorption fields, 5.5% as "Somewhat Limited", and 94.5% as "Very Limited".
How often should I pump my septic tank in Washington 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. Some counties in Missouri have mandatory pumping schedules — check with your local health department.
Can I install a conventional septic system in Washington County?
It depends on your specific site. USDA soil data shows that 94.5% of soils in Washington County are rated "Very Limited" for septic absorption fields, while only 0% 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 ($700-$1400) and soil evaluation are required before the county will approve a system design.
How long does a septic system last in Washington County?
A well-maintained septic system in Washington 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 (Washington 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