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Septic Systems in New Hampshire: What Homeowners Should Know
We refer septic contractors in the Nashua region, the Salem, Derry and Londonderry area, Manchester and Bedford, and the Seacoast from Portsmouth to Rochester. NHDES approves every system, and towns can add rules of their own, so each town page covers both as far as official sources let us confirm them. Call (978) 486-7980 or send the form. A person reads every request and replies with what happens next.
- Free for homeowners
- NH septic rules in plain English
- Nashua to the Seacoast
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Service area
New Hampshire towns we cover
In New Hampshire, NHDES approves septic designs and inspects new systems, while towns handle building permits and may set their own septic standards. Each town page covers who to call locally, any town rules on top of the state's, where public sewer reaches, and the lakes, rivers and aquifers the town protects. Towns without a page yet are still in our area; send a request from any of them.
Nashua Region
Salem, Derry & Londonderry
Manchester & Bedford
Portsmouth, Dover & Rochester
State rules
The state laws that shape a New Hampshire septic job
Two approvals from NHDES. The NHDES Subsurface Systems Bureau reviews septic designs, and NHDES says that before you use a system you need both an Approval for Construction and an Approval for Operation (NHDES septic systems). The system has to be built in strict accordance with the approved plans and inspected before it is covered or used; NHDES inspects within seven business days of notice (RSA 485-A:29).
The application. The state fee is $450 per application for a waste disposal system (as of November 2026), and NHDES acts within 15 working days once an application is complete (RSA 485-A:30 and 485-A:31). A construction approval expires four years after it is issued if no inspection is requested (Env-Wq 1004.13).
Designers and installers. Plans must be prepared and signed by someone holding an NHDES permit for the work (RSA 485-A:35), and no one may be in the business of installing septic systems without an NHDES installer's permit. An owner replacing or repairing the system at his or her own home is exempt from the installer permit but must still follow NHDES rules (RSA 485-A:36). Designer and installer permits run two years, from January 1 of an odd year to December 31 of the next even year (NHDES designers and installers).
Adding load or going year-round. Before expanding a house or changing its use in a way that adds load to the system, such as adding bedrooms, the owner must apply to NHDES and show the system meets the state's requirements or the town's minimum standards, whichever is stricter, or submit a new design (RSA 485-A:38). Converting a seasonal home to full-time use needs an approval for construction first (NHDES).
Failed systems. State law defines failure as a system that does not properly contain or treat sewage, including discharge onto the ground or into surface water, or a disposal area sitting in the seasonal high groundwater (RSA 485-A:2). Owners must operate and maintain a system so it doesn't cause a nuisance or health hazard, and NHDES may inspect and issue compliance orders (RSA 485-A:37).
Selling a house. New Hampshire has no statewide septic inspection at sale apart from the developed-waterfront rule in RSA 485-A:39. Under that rule, when any part of the system is within 250 feet of the reference line, the buyer generally hires a New Hampshire licensed septic system evaluator before the transfer (or instead replaces or repairs the system within 180 days after it), and a failing system must be replaced within 180 days after it (RSA 485-A:39).
Septage haulers. Hauling septage over public roads takes an NHDES septage hauler permit, and permitted trucks show the hauler's name and phone number and an NHDES permit plate (Env-Wq 1600).
Contracts. The Attorney General's office advises a written contract with the scope, materials, total price and payment schedule before any work or payment, and calls a down payment over 50% a warning sign (NH Attorney General). Complaints go to the Consumer Protection Hotline at 1-888-468-4454 (Consumer Protection Hotline).
Digging. Excavation needs notice to Dig Safe at least 72 hours ahead, not counting weekends and legal holidays, and no more than 30 days ahead, with the dig area marked in white (RSA 374:51). Dig Safe is free at 811 (Dig Safe).
Last verified November 2026. Fees, restrictions and deadlines on this page are due for re-checking by November 2027.
Lakes, rivers and records
Shoreland setbacks, local rules and your system's file
Shoreland setbacks. Near ponds, lakes, estuaries and the ocean, septic systems must sit at least 125 feet from the reference line in porous sand and gravel, 100 feet where restrictive layers are within 18 inches of the surface, and 75 feet elsewhere; the setback from rivers is 75 feet. A replacement system has to meet those setbacks to the maximum extent feasible (RSA 483-B:9). Projects in the protected shoreland typically need an NHDES shoreland permit, and NHDES takes questions at (603) 271-2147 (NHDES protected shoreland).
Town rules. Towns may impose more stringent standards for developed waterfront property (RSA 485-A:29, IV), and when load increases the stricter of the state's or the town's standards applies (RSA 485-A:38). Check with your town before planning work.
Looking up a system. NHDES says septic system files can be found on OneStop, its searchable environmental database (NHDES OneStop).
Care. NHDES says homeowners should generally have the system inspected every three years by a licensed contractor, and that tanks should be pumped when necessary, typically every three to five years (NHDES SepticSmart Week).
What we refer
Septic jobs, explained for New Hampshire homeowners
Pumping & Maintenance
Routine tank pumping, filter cleaning and the records your board of health or town may ask for.
Septic Inspections
Title 5 inspections before a Massachusetts sale, and system evaluations for New Hampshire buyers and owners.
Repair & Leach Field Replacement
Broken baffles, failed pumps, backups and leach fields that no longer take water, permitted the way your town requires.
New System Design & Installation
A licensed designer or engineer draws the plan, the town or state approves it, and a permitted installer builds it.
FAQ
New Hampshire septic questions
Do I need a septic inspection to sell my house in New Hampshire?
New Hampshire has no statewide septic inspection at sale apart from the developed-waterfront rule in RSA 485-A:39, which applies when any part of the system is within 250 feet of the reference line of the water.
Does a septic installer need a license in New Hampshire?
It needs a state permit. Anyone in the business of installing septic systems needs an NHDES installer's permit, and plans must be signed by someone holding an NHDES designer permit. Septage haulers need an NHDES hauler permit. Ask the contractor for its permit numbers.
Can I turn a seasonal camp into a year-round home?
Not before NHDES approves it. NHDES says an approval for construction must be obtained before converting a structure from seasonal to full-time occupancy.
Where can I find the approvals for my existing system?
NHDES says septic system files can be found on OneStop, its searchable database of environmental records.
What does it cost me to use New England Septic Pros?
Nothing. The request and the referral are free; the contractor prices the work.