Iowa · Iowa Administrative Code 567 Chapter 69
Iowa DNR writes the rule and county boards of health administer permitting, with county sanitarians performing evaluations.
Minimum tank
One to three bedroom dwelling.
Design flow
Held two days for settling.
Cost index
Regional labour and permits.
Sets the design flow and the legal minimum.
Code sizes on bedrooms, not people.
Used to size the matching drainfield. Unsure? Sandy loam is the common default.
Deep loess and glacial till, generally silty clay loam with slow to moderate percolation. Northeast Iowa has shallow bedrock and karst. Alluvial soils along the rivers drain faster.
Conventional trenches, and a heavy use of secondary treatment. Iowa requires secondary treatment before discharge in many circumstances, which pushes designs toward sand filters and aerobic units more than in neighbouring states.
| Dwelling | Design flow | Minimum tank | With disposal |
|---|---|---|---|
| 1 bedroom | 300 gpd | 1,000 gal | 1,250 gal |
| 2 bedrooms | 300 gpd | 1,000 gal | 1,250 gal |
| 3 bedrooms | 450 gpd | 1,000 gal | 1,250 gal |
| 4 bedrooms | 600 gpd | 1,250 gal | 1,500 gal |
| 5 bedrooms | 750 gpd | 1,500 gal | 1,750 gal |
Iowa requires a time of transfer inspection when a property with a private sewage system is sold — a distinctive requirement that catches many sellers by surprise. Certified inspectors perform it and non-compliant systems must be upgraded.
The state sets a floor. These Iowa counties are where the largest septic populations sit, and where local requirements most often exceed it.
| County | What makes it different |
|---|---|
| Polk | Des Moines metro fringe |
| Linn | Cedar Rapids area |
| Dubuque | Northeast Iowa karst and bedrock |
| Scott | Mississippi river valley soils |
| Dallas | Rapid suburban growth west of Des Moines |
A three-bedroom home at 150 gallons per bedroom produces 450 gallons per day of design flow. On sandy loam that needs roughly 750 square feet of absorption area. On clay loam it rises to about 2,250 square feet, and on clay a conventional field is usually not permitted at all. Run your own soil class through the drainfield calculator.
Iowa's time of transfer inspection effectively forces system evaluation at every property sale. Use the pump schedule calculator to work out the interval for your tank size and household.
Regional labour and permit costs in Iowa run about 95% of the national baseline. Here is what typical installations land at for a three-bedroom home:
| System type | Typical installed cost in Iowa | When it applies |
|---|---|---|
| Conventional gravity | $8,600 – $15,200 | Good soil, adequate depth to water |
| Chamber system | $9,500 – $17,500 | Alternative to gravel trenches |
| Mound system | $16,300 – $31,900 | Shallow water table or thin soil |
| Aerobic treatment | $13,800 – $27,400 | Clay soil or small lots |
| Tank pump-out (service) | $300 – $620 | Every 3–5 years |
Replacing an existing system costs more than these figures — old-system removal and re-permitting add to every line. The replacement cost calculator covers that case, and the cost estimator adjusts all of the above for your bedroom count and soil.
Verify before you build. The figures above are state minimums compiled for planning, drawn from Iowa Administrative Code 567 Chapter 69, Private Sewage Disposal Systems. County and health district rules routinely exceed them, code text changes, and only Iowa DNR — Onsite Wastewater Systems or your local health department can confirm what applies to your parcel.
Send your sizing numbers to installers who work under Iowa rules every day.