Septic Systems in Gilliam County, OR

Regulations, costs, soil data & local providers

Pop. 1,995 ~32% on septic ~255 septic homes Well drained soil

Septic pumping in Gilliam County, Oregon costs $300-$650 (avg $450). A new septic system installation costs $6,250-$12,550. USDA soil data rates 0% of county soils as suitable for septic absorption fields. Approximately 255 homes in this county use septic systems.

Septic System Costs in Gilliam County

ServiceLowAverageHigh
Pumping / Cleaning$300$450$650
Routine Inspection$250$350$500
Real Estate Inspection$400$600$850
Minor Repair$750$1,100$5,450
Conventional Installation$6,250$8,950$12,550
Aerobic System Installation$11,750$16,800$23,500
Drainfield Replacement$6,250$8,950$12,550
Perc Test$950$1,350$1,900

Cost estimates based on regional market data for Gilliam County, Oregon. Actual costs depend on system type, site conditions, and provider.

Soil & Septic Suitability in Gilliam County

Drainage Class
Well drained
Hydrologic Group
C
Unique Soil Types
81
Avg Bedrock Depth
3 ft

Dominant Soil Types

Soil SeriesCoverageDrainageHydro Group
Ritzville 781 Well drained B
Sagehill 622 Well drained B
Olex 615 Well drained B
Morrow 529 Well drained C
Warden 497 Well drained B

Septic Tank Absorption Field Suitability

USDA NRCS rates soil suitability for septic absorption fields across this county:

Not Limited (Good)0%
Somewhat Limited20.2%
Very Limited79.8%

Overall rating: Very limited

Source: USDA NRCS Soil Survey Geographic Database (SSURGO)

Groundwater & Water Table in Gilliam County

Monitoring Wells
2
Avg Depth to Water
119 ft
Median Depth
119 ft
Shallowest Recorded
34 ft

Water table depths in this county are generally favorable for conventional septic systems.

Source: USGS National Water Information System. Based on 2 measurements from monitoring wells.

Septic Regulations & Permits in Gilliam 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 Gilliam County health department for current permit requirements, fees, and approved system types.

Septic System FAQ for Gilliam County

How much does septic pumping cost in Gilliam County?
Septic pumping in Gilliam County, Oregon typically costs between $300 and $650, with an average of $450. 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 Gilliam County?
A conventional septic system installation in Gilliam County typically costs $6,250-$12,550. An aerobic treatment unit (ATU) costs $11,750-$23,500. 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 Gilliam 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 Gilliam County health department for current requirements and fees.
What soil types are in Gilliam County and how do they affect septic systems?
Gilliam County has predominantly Ritzville, Sagehill, Olex 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, 20.2% as "Somewhat Limited", and 79.8% as "Very Limited".
How often should I pump my septic tank in Gilliam 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 Oregon have mandatory pumping schedules — check with your local health department.
Can I install a conventional septic system in Gilliam County?
It depends on your specific site. USDA soil data shows that 79.8% of soils in Gilliam 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 ($950-$1900) and soil evaluation are required before the county will approve a system design.
How long does a septic system last in Gilliam County?
A well-maintained septic system in Gilliam 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 (Gilliam 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.

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Quick Facts

Population1,995
Est. Septic Homes255
Avg Pumping Cost$450
Drainage ClassWell drained
Septic SuitabilityVery limited

More in Oregon

Sherman County Morrow County Wheeler County Wasco County Jefferson County Crook County

Common Septic Services

Pumping: $300-$650
Inspection: $250-$500
Repair: $750-$5,450
Installation: $6,250-$12,550

Data last updated: 2026-04-13