Our modeled range for septic pumping in Lewis and Clark County, Montana is $350-$700. A modeled conventional installation range is $6,700-$13,450. The site model estimates approximately 7,097 homes may use septic systems; this is not a county count.
Septic System Costs in Lewis and Clark County
| Service | Low | Average | High |
|---|---|---|---|
| Pumping / Cleaning | $350 | $500 | $700 |
| Routine Inspection | $250 | $350 | $500 |
| Real Estate Inspection | $450 | $650 | $900 |
| Minor Repair | $850 | $1,200 | $5,900 |
| Conventional Installation | $6,700 | $9,600 | $13,450 |
| Aerobic System Installation | $12,600 | $18,000 | $25,200 |
| Drainfield Replacement | $6,700 | $9,600 | $13,450 |
| Perc Test | $1,000 | $1,450 | $2,050 |
Modeled estimates derived from national reference ranges and a regional multiplier, not observed local quotes. Actual costs depend on system type, site conditions, permits, and provider.
Groundwater & Water Table in Lewis and Clark County
Monitoring Wells
4
Avg Depth to Water
44.4 ft
Median Depth
38 ft
Shallowest Recorded
26.4 ft
Water table depths in this county are generally favorable for conventional septic systems.
Source: USGS National Water Information System. Based on 66 measurements from monitoring wells.
Septic System FAQ for Lewis and Clark County
How much does septic pumping cost in Lewis and Clark County?
Our modeled pumping range for Lewis and Clark County, Montana is $350-$700, with a modeled midpoint of $500. This is not an observed local quote. Actual cost varies by tank size, access, travel distance and tank condition.
How much does a new septic system cost in Lewis and Clark County?
Our modeled conventional-installation range for Lewis and Clark County is $6,700-$13,450; the modeled aerobic-system range is $12,600-$25,200. These are planning indicators, not observed local quotes. A site evaluation and provider estimate are needed.
Do I need a permit for a septic system in Lewis and Clark County?
Permit requirements depend on the work, property and responsible authority. Review the verified official-source summary on this page, then contact the authority directly for the current application, exemptions, fees, site-evaluation requirements and inspection steps before work begins.
What soil types are in Lewis and Clark County and how do they affect septic systems?
Contact the county health department for soil evaluation requirements.
How often should I pump my septic tank in Lewis and Clark 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 7,097 septic systems in Lewis and Clark County, there are many local providers offering regular pumping services.
How long does a septic system last in Lewis and Clark County?
A well-maintained septic system in Lewis and Clark 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. Regular pumping every 3-5 years and avoiding excess water usage are the two most effective ways to extend system life.
Data last updated: 2026-08-26