Massachusetts · 310 CMR 15.000
MassDEP writes Title 5 and local boards of health administer it, with authority to impose stricter local requirements.
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.
Glacial till, outwash sand on the Cape and Islands, and ledge inland. Cape Cod's sandy soil percolates freely but sits over a sole source aquifer, which is why nitrogen rather than percolation drives the rules there.
Conventional trenches and leaching chambers, with innovative/alternative technology for nitrogen reduction increasingly required in nitrogen sensitive areas, particularly on Cape Cod.
| Dwelling | Design flow | Minimum tank | With disposal |
|---|---|---|---|
| 1 bedroom | 220 gpd | 1,500 gal | 1,750 gal |
| 2 bedrooms | 220 gpd | 1,500 gal | 1,750 gal |
| 3 bedrooms | 330 gpd | 1,500 gal | 1,750 gal |
| 4 bedrooms | 440 gpd | 1,500 gal | 1,750 gal |
| 5 bedrooms | 550 gpd | 1,500 gal | 1,750 gal |
Title 5 requires a system inspection at property transfer — the most consequential inspection requirement in the country. A failed inspection must be corrected, and this shapes the entire Massachusetts real estate process for septic properties.
The state sets a floor. These Massachusetts counties are where the largest septic populations sit, and where local requirements most often exceed it.
| County | What makes it different |
|---|---|
| Barnstable | Cape Cod; sole source aquifer and nitrogen requirements |
| Plymouth | Large septic population, sandy soils |
| Worcester | Inland till and ledge |
| Essex | Coastal and inland mix |
| Bristol | Southeastern Massachusetts, nitrogen sensitive areas |
| Dukes | Martha's Vineyard, severe nitrogen constraints |
A three-bedroom home at 110 gallons per bedroom produces 330 gallons per day of design flow. On sandy loam that needs roughly 550 square feet of absorption area. On clay loam it rises to about 1,650 square feet, and on clay a conventional field is usually not permitted at all. Run your own soil class through the drainfield calculator.
Title 5 inspection is required at transfer of title, and pumping records form part of the inspection. Use the pump schedule calculator to work out the interval for your tank size and household.
Regional labour and permit costs in Massachusetts run about 142% of the national baseline. Here is what typical installations land at for a three-bedroom home:
| System type | Typical installed cost in Massachusetts | When it applies |
|---|---|---|
| Conventional gravity | $12,800 – $22,700 | Good soil, adequate depth to water |
| Chamber system | $14,100 – $26,100 | Alternative to gravel trenches |
| Mound system | $24,300 – $47,700 | Shallow water table or thin soil |
| Aerobic treatment | $20,500 – $40,900 | Clay soil or small lots |
| Tank pump-out (service) | $450 – $920 | 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 310 CMR 15.000, the State Environmental Code Title 5. County and health district rules routinely exceed them, code text changes, and only Massachusetts DEP — Title 5 Program or your local health department can confirm what applies to your parcel.
Send your sizing numbers to installers who work under Massachusetts rules every day.