Michigan septic rules
Michigan septic tank size & cost
Michigan has no state tank table — your county is the rule. A typical new 3-bedroom system in Michigan runs about $7,600–$12,100 installed by our line-by-line estimate. Below: the state's actual size rule, the full table, and where every number comes from.
Rule: Michigan Criteria for Subsurface Sewage Disposal (state baseline, referenced by R 323.2210); county sanitary codes set the binding numbers · Administered by 45 local health departments covering Michigan's 83 counties · Read the official text · Checked 2026-11-10
Michigan's rule, in plain words
Michigan has no statewide bedroom-to-tank table. Each county health department writes its own sanitary code, and the numbers genuinely differ county to county — any website showing one 'Michigan' tank size is making it up.
Michigan never wrote a statewide bedroom-to-tank table. The state publishes design criteria, but the binding numbers live in the sanitary codes of 45 local health departments covering 83 counties — and they genuinely differ. In the Central Michigan district (six counties), a 2-bedroom home needs 750 gallons; twenty miles of county lines away, Grand Traverse County's table starts the same home at 1,000.
So this page does the only honest thing: it shows the state framework, prints one real county district's full table as an example, and tells you plainly that any website showing a single 'Michigan' tank size is inventing it. Your county health department's number is the only one that counts.
The Michigan size table
One real example: Central Michigan District Health Department (Arenac, Clare, Gladwin, Isabella, Osceola, Roscommon)
| Bedrooms | Minimum tank (gal) |
|---|---|
| 1 | 750 |
| 2 | 750 |
| 3 | 1,000 |
| 4 | 1,250 |
| 5+ | +250 per extra bedroom |
Sanitary Code Art. IV §B.5. Capacity must also hold at least 36 hours of design flow; the absolute floor is 750 gal.
Garbage disposal: Varies by county: some add a flat amount (Marquette +250 gal), some start disposals on a higher row (Grand Traverse), some say nothing. Check your county code.
Find your county health department before you buy anything — in Michigan the county number is the only number that counts.
Check your Michigan home
State minimum — your county can require more. Estimate this system's cost →
What a Michigan system costs
Our estimator prices a conventional 3-bedroom system in Michigan (typical-cost area, 1,000-gal tank) at $7,600–$12,100 installed, assembled from a soil test, the permit, the tank at published prices, drainfield material, fittings and labor. Build your own estimate →
How Michigan compares (3-bedroom minimum)
Full ten-state chart: septic tank size chart.
Other states we've checked
Get an email if Michigan's rule changes
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