Septic system requirements in New Hampshire
What landplan.io applies when it designs a septic system in New Hampshire: the system types allowed, tank sizes, setbacks and soil loading rates, with what septic products cost there.
Updated
Design a septic system for an address in New Hampshire
Reviewed landplan.io designs by New Hampshire's own rules, which our staff reviewed against the state's regulations. Last published 5 October 2026.
Septic systems allowed in New Hampshire
The system types landplan.io permits in New Hampshire:
- Elevated Sand Mound System
- Subsurface Pressure Trench System
- Subsurface Trench System
- Infiltrator Advanced Treatment Leachfield
- Infiltrator Advanced Enviro-Septic® (AES)
- Discharging System
Septic tank size in New Hampshire
The daily design flow of a home: 150 gal/day per bedroom, at least 240 gal/day. The septic tank is sized from that flow:
| Daily design flow | Minimum tank |
|---|---|
| up to 240 gal/day | 1,000 gallons |
| 240 to 360 gal/day | 1,500 gallons |
| 360 to 600 gal/day | 2,000 gallons |
| 600 to 720 gal/day | 2,500 gallons |
| 720 to 840 gal/day | 2,750 gallons |
| 840 to 920 gal/day | 3,000 gallons |
| 920 to 1,040 gal/day | 3,250 gallons |
Septic setbacks in New Hampshire
| From | To | Distance |
|---|---|---|
| Polygon | Existing Septic Component to be Abandoned | 5 ft |
These are the values the landplan.io design engine applies in New Hampshire. Confirm a design with the New Hampshire health department or your county's before you build.
Parcel data in New Hampshire
landplan.io has parcel boundaries for 10 of New Hampshire's 10 counties: the counties where 100% of the state's people live. Type an address there and the design starts from the parcel.
Septic companies, designers and jobs in New Hampshire
- Septic companies and distributors in New Hampshire (19)
- Septic designers in New Hampshire
- Septic design jobs in New Hampshire
Where the rules come from
The regulations and documents landplan.io's New Hampshire rules are read from:
Septic rules by county in New Hampshire
- Belknap County
- Carroll County
- Cheshire County
- Coos County
- Grafton County
- Hillsborough County
- Merrimack County
- Rockingham County
- Strafford County
- Sullivan County
Questions
What septic systems are allowed in New Hampshire?
landplan.io permits these system types in New Hampshire: Elevated Sand Mound System, Subsurface Pressure Trench System, Subsurface Trench System, Infiltrator Advanced Treatment Leachfield, Infiltrator Advanced Enviro-Septic® (AES) and Discharging System.
What size septic tank do I need in New Hampshire?
landplan.io sizes the septic tank in New Hampshire from the daily design flow: up to 240 gal/day: 1,000 gallons; 240 to 360 gal/day: 1,500 gallons; 360 to 600 gal/day: 2,000 gallons; larger flows need larger tanks. A home's design flow is 150 gal/day per bedroom, at least 240 gal/day.
Does landplan.io have parcel data in New Hampshire?
Yes, for 10 of New Hampshire's 10 counties.