What the drain field does, and what the state requires of it
The drain field is where the tank's liquid goes to be treated by soil. EGLE says wastewater from the middle third of the tank spreads through the field and percolates into the soil, and that a properly sized field sits in the upper soil profile with unsaturated soil above the seasonal high water table. The state Criteria turn that into numbers: at least 4 feet between the bottom of the trench or bed and the high groundwater elevation, a percolation rate of 45 minutes per inch or faster, and absorption systems at least 10 feet from property lines and 15 feet from foundations. These are minimums, and counties can be stricter. Where the soil is shallow or the water table high, EPA says mound systems or drip distribution are the options, and both need maintenance.
What drain field work costs in Michigan: the evidence so far
Our estimate for repairing a drain field is $890 to $6,025 per repair, and for a full replacement $2,675 to $18,100 per replacement. Both are models, not quotes, built from one published national range each and Michigan's operating engineer wage ratio to the US (1.05). The table also holds the servicer wage and the two whole-system ranges that bracket the question.
| Item | Figure | What it is |
|---|---|---|
| Estimated range, not a quote | $890 to $6,025 per repair | Built from one national published range, adjusted by the Michigan operating engineer median wage ratio (1.05). No Michigan septic company published a range we could count. |
| Estimated range for a full drain field replacement, not a quote | $2,675 to $18,100 per replacement | Built from one national published range, adjusted by the Michigan operating engineer median wage ratio (1.05). No Michigan septic company published a range we could count. |
| Septic tank servicer wage, Michigan mean | $24.85 an hour | What Michigan septic tank servicers are paid (BLS, May 2025, statewide), not what you are charged. |
| Repair or replace a malfunctioning conventional system (U.S. EPA) | $5,000 to $15,000 | EPA's national range, undated. Alternative systems cost more, and EPA gives no figure for them. |
| Replacement septic system (Michigan EGLE) | $8,000 to $30,000 | From EGLE's July 2025 news release on septic loans. EGLE gives no source or date for the range. |
How we estimate costs: the Estimated range row is a model, not a quote. It takes one published national range for this job (a cost guide from a third-party site that we have not verified and do not cite) and multiplies it by Michigan's operating engineer median wage ratio to the US (1.05, BLS 2025 data). No permit or evaluation fee is added: the county rows are shown as the schedules print them. The wage and fee rows are what workers are paid and what a county charges, and neither is a price you will be quoted. We have not collected Michigan septic quotes, and one company's published pumping price is not a range. Your tank, soil and site move a real quote outside any range, so get written quotes. Full method. Prices as of Oct 19, 2026.
What damages a field
Solids that leave a tank that was not pumped on time clog the field, EPA says. Roots are a second cause in Michigan: EGLE says to keep walnut, maple, cottonwood, aspen and willow trees away from the system, and to keep large shrubs back as well. Weight on the field does harm too. EGLE says not to park or drive on any part of the system or put dumpsters or heavy machinery on it, and to point gutter downspouts away. Age matters as well: EPA says a field over 25 to 30 years old can develop a thickened biomat that causes ponding, surfacing or backup, and that owners should plan an upgrade. After a flood, EGLE says to mark the system and keep vehicles off it.
Setbacks by county: the state sets a floor, not the answer
EGLE's FAQ says the state well code requires 50 feet between a single-family well and a septic system and that surface-water distance is no less than 50 feet, while the 1994 Criteria say absorption systems stay 100 feet from surface water. The county code decides, and the numbers differ. Oakland County reads 50 feet to a well and to surface water. Genesee County requires 50 feet to a well and surface water but 200 feet to Type I and IIa wells. Saginaw County uses 50 feet to a deep well, 100 feet to a shallow well and 75 feet to a lake or stream. Monroe County uses 50 feet to a drilled well and 100 feet to surface water. Ottawa County also requires a reserve area for a future replacement field at least as large as the first.
Frozen and saturated ground
The Criteria say construction should not happen when soils are saturated by heavy rain or snowmelt, or frozen, unless the reviewing agency approves. Genesee County bars field installation from December 15 to April 15 without written consent, and St. Clair County bars it from December 1 to March 1 without approval.
When a drain field problem cannot wait
- Sewage is surfacing in the yard or backing up inside.
- The field is wet and foul after a flood: keep people and vehicles off it.
- A bright green strip over the field with no surfacing or backup: book an inspection soon.
- A tree near the field: plan its removal, because EGLE links roots to failure.
Before you call
- Keep vehicles and heavy items off the field and mark its edges.
- Point downspouts and sump discharge away from it, and fix leaking fixtures.
- Note where the wet spot is, when it appears and whether it follows rain.
- Ask the county for the as-built drawing, which shows where the field lies.
Permits for field repair or replacement
The county health department issues the permit and inspects before the trench is covered. Its fee for repair or replacement appears on the repair page. Saginaw, Ottawa, St. Clair and Jackson counties charge double for work started without a permit.
A tool for this job
Septic failure signs and drain field care
Pick the symptom that fits best and say when the tank was last pumped. The tool uses EGLE's definition of a failed system and EPA's guidance to say if you should call your county health department first or book an inspection, and it ends with drain field care that applies either way. It is a guide to the likely next step, not a diagnosis.
Open the toolQuestions people ask
What causes a septic drain field to fail?
Solids, roots, excess water and age, according to EGLE and EPA. EGLE calls root intrusion one of the leading causes of failure in Michigan, and EPA says a field over 25 to 30 years old can develop a thickened biomat.
Can a drain field be repaired?
Sometimes, but significant root intrusion or a clogged field can require replacing the field. Both EGLE and EPA say so. A county permit comes first.
How far must a drain field be from a well in Michigan?
The state well code sets 50 feet for a single-family well, and some county codes require more. Genesee County requires 200 feet to Type I and IIa wells, and Saginaw County requires 100 feet to a shallow well.
How deep does a septic system need to be?
The Michigan Criteria set separation from groundwater, not a burial depth: at least 4 feet from the bottom of the trench or bed to high groundwater. Counties set their own design details, so ask yours.
How much does drain field repair cost in Michigan?
Our estimate for a drain field repair is $890 to $6,025 per repair, and for a full replacement $2,675 to $18,100 per replacement. Both are models, not quotes. EPA says $5,000 to $15,000 nationally to repair or replace a conventional system, and EGLE says $8,000 to $30,000 for a Michigan replacement.
- EGLE: Onsite wastewater management Read Oct 19, 2026.
- Michigan Criteria for Subsurface Sewage Disposal Read Oct 19, 2026.
- EPA: Types of Septic Systems Read Oct 19, 2026.
- EPA: Resolving Septic System Malfunctions Read Oct 19, 2026.
- EGLE FAQ: Septic systems Read Oct 19, 2026.
- EPA: Why Maintain Your Septic System Read Oct 19, 2026.
- Oakland County Sanitary Code, January 2026 (PDF) Read Oct 19, 2026.
- Genesee County Sewage Disposal Construction Standard Read Oct 19, 2026.
- Saginaw County Environmental Health Code Read Oct 19, 2026.
- Chapter 5 Read Oct 19, 2026.
- County of Ottawa Environmental Health Regulations (PDF), Art. IX.H Read Oct 19, 2026.
- Environmental Health Fees | Ottawa County, MI Read Oct 19, 2026.
- SCHD Environmental Health Fees (effective October 1, 2026) Read Oct 19, 2026.
- Environmental Health Service Fees (as of 10/01/2026) Read Oct 19, 2026.
- FY2026 Fee Schedule EH Read Oct 19, 2026.
- EGLE news release, July 29 2025 Read Oct 19, 2026.
- O*NET OnLine (U.S. Department of Labor), Michigan wages, Operating Engineers and Other Construction Equipment Operators (SOC 47-2073), republishing BLS OEWS 2025 Read Oct 19, 2026. The source implies this without saying it, so check with the source before you act on it.
- SepticMatch: how we estimate costs (editorial policy) Read Oct 19, 2026.
- U.S. Bureau of Labor Statistics, OEWS May 2025: septic tank servicers and sewer pipe cleaners (SOC 47-4071), Michigan Read Oct 19, 2026.