Missouri septic rules
Missouri septic tank size & cost
In Missouri, who issues your permit depends on your county. A typical new 3-bedroom system in Missouri runs about $6,900–$11,100 installed by our line-by-line estimate. Below: the state's actual size rule, the full table, and where every number comes from.
Rule: 19 CSR 20-3.060(4)(B), Table 4 · Administered by Missouri Department of Health and Senior Services (DHSS) · Read the official text · Checked 2026-11-10
Missouri's rule, in plain words
Missouri's state table (19 CSR 20-3.060, Table 4) is straightforward — 1,000 gallons through three bedrooms, 1,250 at four, 1,500 at five, and a formula beyond that (capacity = 1.5 × design flow + 500). A detail in the table's own footnote defeats a common myth: those capacities already include garbage disposals and other water-using appliances, so there is no disposal add-on in Missouri.
The wrinkle is administration: roughly half of Missouri's counties run their own permit ordinances and half operate under state authority, so fees and inspectors vary. A state fee-schedule change is also pending in 2026 — we show permit costs as a range until it settles.
The Missouri size table
| Bedrooms | Minimum tank (gal) | With garbage disposal |
|---|---|---|
| 1 | 1,000 | 1,000 |
| 2 | 1,000 | 1,000 |
| 3 | 1,000 | 1,000 |
| 4 | 1,250 | 1,250 |
| 5 | 1,500 | 1,500 |
| 6 | — | — |
Six or more bedrooms are sized by formula in (4)(B)17: capacity = 1.5 × design flow + 500 gal. A 6-bedroom home at the standard 150 gpd/bedroom flow works out to 1,850 gal.
Garbage disposal: No add-on: Table 4's own footnote says its capacities already include garbage disposals and other water-using appliances.
About half of Missouri's counties issue permits under a local ordinance and half under state authority — your permit fee and inspector depend on which side your county sits.
Missouri's state application fee schedule is in flux (a 2026 rule change is pending) — permit fees on this page are shown as a range.
Check your Missouri home
State minimum — your county can require more. Estimate this system's cost →
What a Missouri system costs
Our estimator prices a conventional 3-bedroom system in Missouri (lower-cost area, 1,000-gal tank) at $6,900–$11,100 installed, assembled from a soil test, the permit, the tank at published prices, drainfield material, fittings and labor. Build your own estimate →
How Missouri compares (3-bedroom minimum)
Full ten-state chart: septic tank size chart.
Other states we've checked
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