Michigan · Part 117, PA 368 of 1978
Septic system requirements in Michigan
Tank sizes, drainfield rules, setbacks, permits, and real costs — pulled from Michigan's own code rather than a national average.
- 3-bedroom tank
- 1,000 gal
- Design flow
- 150 gpd/BR
- Typical install
- $8,000–$22,000
- Permit fee
- $200–$900
- Well setback
- 50 ft
- Permitted by
- County / local
Septic tank sizes required in Michigan
Michigan sizes systems on a design flow of 150 gallons per day per bedroom. The tank must meet both the bedroom table below and a 2× daily-flow detention requirement — whichever produces the larger number governs.
| Bedrooms | Design flow | Code minimum | Recommended |
|---|---|---|---|
| 1 bedroom | 150 gpd | 1,000 gal | 1,000 gal |
| 2 bedrooms | 300 gpd | 1,000 gal | 1,000 gal |
| 3 bedrooms | 450 gpd | 1,000 gal | 1,000 gal |
| 4 bedrooms | 600 gpd | 1,000 gal | 1,250 gal |
| 5 bedrooms | 750 gpd | 1,250 gal | 1,500 gal |
| 6 bedrooms | 900 gpd | 1,500 gal | 2,000 gal |
Source: Part 117, PA 368 of 1978. The recommended column rounds the governing requirement up to a tank size manufacturers actually stock.Run your own numbers →
Drainfield size and cost by soil type
For a three-bedroom home in Michigan at 450 gpd. This single table explains most of the variation between quotes — the area scales inversely with how fast your soil accepts water, and the drainfield is the largest line item in the job.
| Soil | Loading rate | Absorption area | With reserve | Typical total install |
|---|---|---|---|---|
| Medium sand | 0.8 gpd/ft² | 563 ft² | 1,126 ft² | $11,300 |
| Sandy loam | 0.5 gpd/ft² | 900 ft² | 1,800 ft² | $14,200 |
| Loam | 0.4 gpd/ft² | 1,125 ft² | 2,250 ft² | $16,200 |
| Silt loam | 0.3 gpd/ft² | 1,500 ft² | 3,000 ft² | $19,500 |
| Clay loam | 0.2 gpd/ft² | 2,250 ft² | 4,500 ft² | $26,100 |
Estimates use Michigan's cost index of 0.98× the national average. Build a line-item estimate →
Permits and who issues them
Michigan has no statewide sanitary code for onsite systems. County health departments write and enforce their own ordinances against EGLE minimum criteria.
| Permit required | Yes |
|---|---|
| Typical fee | $200 – $900 |
| Soil evaluation | Required before permit |
| Licensed installer | Not required statewide |
| Turnaround | 2–6 weeks |
| Ongoing inspection | Point-of-sale inspection required by many counties, not by the state |
| Reserve area | 100% replacement area required |
Minimum setback distances
Measured horizontally from the drainfield unless noted. Local rules are frequently stricter, and on a small lot these numbers — not the soil — often decide the layout.
| Private water well | 50 ft |
|---|---|
| Property line | 10 ft |
| Surface water | 50 ft |
| Building foundation | 10 ft |
Regulatory contact
Michigan EGLE — Onsite Wastewater Management
www.michigan.gov · 517-284-6500
What makes septic hard in Michigan
Michigan is the only state without a statewide onsite sewage code. What is permitted depends entirely on your county ordinance, and neighbouring counties genuinely differ.
High water tables across the lake plains and the northern counties limit trench depth.
Lakefront lots face both setback pressure and nutrient-loading concerns.
Things that catch people out
- Many counties — but not all — require a point-of-sale inspection. Check yours before listing, because the state will not tell you.
- Because there is no state code, a design that passed in one county can be rejected outright in the next.
Michigan septic questions
What size septic tank do I need in Michigan?
A three-bedroom home in Michigan requires a minimum 1,000 gallon tank under Part 117, PA 368 of 1978. Design flow is 150 gallons per day per bedroom, and the tank must also hold 2 times daily flow, so the practical recommendation is 1,000 gallons.
Do I need a permit for a septic system in Michigan?
Yes. Michigan has no statewide sanitary code for onsite systems. County health departments write and enforce their own ordinances against EGLE minimum criteria. Fees typically run $200 to $900, with a turnaround of about 2–6 weeks. A soil evaluation or percolation test is required before a permit is issued.
How much does a septic system cost in Michigan?
A conventional system for a three-bedroom home typically runs $8,000 to $22,000 installed. Soil quality moves this more than anything else — on tight clay requiring a mound, budget two to three times the low end.
How far must a Michigan drainfield be from a well?
50 feet from a private water well. Local rules can be stricter.
Sources
Every figure on this page traces to one of these documents.
- Part 117, PA 368 of 1978 — Michigan Public Health Code — Onsite Wastewater · verified 2026-09-18
- EGLE Criteria — Michigan Criteria for Subsurface Sewage Disposal · verified 2026-09-18