Septic pumping in Multnomah County, Oregon costs $400-$750 (avg $550). A new septic system installation costs $7,750-$15,450. USDA soil data rates 0% of county soils as suitable for septic absorption fields. Approximately 19,570 homes in this county use septic systems.
Septic System Costs in Multnomah County
| Service | Low | Average | High |
|---|---|---|---|
| Pumping / Cleaning | $400 | $550 | $750 |
| Routine Inspection | $300 | $400 | $550 |
| Real Estate Inspection | $500 | $750 | $1050 |
| Minor Repair | $1,000 | $1,400 | $6,800 |
| Conventional Installation | $7,750 | $11,050 | $15,450 |
| Aerobic System Installation | $14,500 | $20,700 | $29,000 |
| Drainfield Replacement | $7,750 | $11,050 | $15,450 |
| Perc Test | $1,150 | $1,650 | $2,300 |
Cost estimates based on regional market data for Multnomah County, Oregon. Actual costs depend on system type, site conditions, and provider.
Soil & Septic Suitability in Multnomah County
Drainage Class
Well drained
Hydrologic Group
C
Unique Soil Types
43
Avg Bedrock Depth
4.2 ft
Dominant Soil Types
| Soil Series | Coverage | Drainage | Hydro Group |
|---|---|---|---|
| Multnomah | 665 | Well drained | B |
| Latourell | 616 | Well drained | B |
| Cascade | 500 | Somewhat poorly drained | C |
| Quatama | 490 | Moderately well drained | C |
| Bull Run | 425 | Well drained | B |
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 Multnomah County
Monitoring Wells
26
Avg Depth to Water
60.1 ft
Median Depth
59.2 ft
Shallowest Recorded
-1.1 ft Shallow Risk
Water table depths in this county are generally favorable for conventional septic systems.
Source: USGS National Water Information System. Based on 741 measurements from monitoring wells.
Septic Regulations & Permits in Multnomah County
State Regulatory Body
Oregon DEQ
Inspection Required for Home Sale
No / Varies
Nitrogen Reduction Areas
No
Advanced Treatment Required
In designated areas
Some counties require time-of-transfer inspection. Authorization required for installers.
Contact the Multnomah County health department for current permit requirements, fees, and approved system types.
Septic System FAQ for Multnomah County
How much does septic pumping cost in Multnomah County?
Septic pumping in Multnomah County, Oregon 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 Multnomah County?
A conventional septic system installation in Multnomah County typically costs $7,750-$15,450. An aerobic treatment unit (ATU) costs $14,500-$29,000. 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 Multnomah County?
Yes. Virtually all counties in Oregon 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 Multnomah County health department for current requirements and fees.
What soil types are in Multnomah County and how do they affect septic systems?
Multnomah County has predominantly Multnomah, Latourell, Cascade soils. The dominant drainage class is Well drained with hydrologic group C. The USDA rates 0% of surveyed soils as "Not Limited" for septic absorption fields, 2.9% as "Somewhat Limited", and 97.1% as "Very Limited".
How often should I pump my septic tank in Multnomah 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 19,570 septic systems in Multnomah County, there are many local providers offering regular pumping services.
Can I install a conventional septic system in Multnomah County?
It depends on your specific site. USDA soil data shows that 97.1% of soils in Multnomah 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 ($1150-$2300) and soil evaluation are required before the county will approve a system design.
How long does a septic system last in Multnomah County?
A well-maintained septic system in Multnomah 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 (Multnomah 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