Drain field in Oakland County: what to know
Article III of the Oakland County Sanitary Code sets minimum isolation distances: 50 feet from a private well to the septic tank and 50 feet from a well to the absorption system, 50 feet to surface water, and 10 feet to property lines and building foundations, with notes that let the Health Officer reduce or increase them. Read the table for your lot, because the county's notes change the numbers.
Permits are valid for two years from issuance and applications for one, and the Health Officer may require plans by a licensed professional engineer. A repair of a field is $221 and a new residential permit $325 on the schedule effective Oct 1, 2026. Anyone digging needs the county's installer license.
Permits for drain field in Oakland County
The county health department issues the permit and inspects before the trench is covered.
Oakland County Health Division, Environmental Health Services. Apply online or at the counter for new residential, replacement or repair permits; construction and final inspections follow. Application valid 1 year; permit valid 2 years; engineer plans can be required. The Oakland County septic rules
Oakland County septic fees
| Item | Amount | Note |
|---|---|---|
| New residential permit, vacant land | $325 | Effective Oct 1, 2026 |
| Repair or replace, residential | $221 | Same schedule |
| Alternative-system technology review | $360 | Same schedule |
| Installer class | $50 | License is $100 a year |
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
Measure from your well to the nearest edge of the field and compare it to the 50-foot line before you plan any addition.
- 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.
What drain field costs
The estimate below is the Michigan-wide one and not an Oakland County price. The same table is on the drain field page. How we estimate costs. Prices as of Oct 19, 2026.
| 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.
Questions about drain field
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.