How much does a septic system cost?

A new septic system runs about $5,000 to $25,000 or more, with a conventional gravity system on the lower end and engineered mound or aerobic systems much higher. The tank, drain field, soil testing, permits, and excavation all factor in.

Can I install a septic system myself?

No. Septic systems are health-code regulated because they treat sewage and can contaminate groundwater if done wrong. They require a perc test, an engineered design, permits, and a licensed installer with heavy equipment, plus a health-department inspection before use.

How long does a septic system last?

A well-maintained septic system can last 20 to 40 years, with the tank often outlasting the drain field. Pumping every 3 to 5 years, keeping heavy vehicles off the field, and limiting what goes down the drain all extend its life significantly.

How often should a septic tank be pumped?

Most households pump the tank every 3 to 5 years, depending on tank size and how many people use it. Regular pumping prevents solids from reaching and clogging the drain field, which is the expensive part to replace.

A percolation test measures how fast water drains through the soil, which determines whether and what kind of septic system a site can support. It is required before a system is designed, since slow-draining soil may need a larger or engineered system.

UPDATED JUNE 2026

Septic System Installation Cost in New Hampshire

Locally calibrated hire vs. DIY cost data for septic system installation projects in New Hampshire. Cited sources, permit requirements, and a full build guide, free.

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HIRE A PRO

$5,200–$26,100

Fully installed, labor + materials

DIY COST

$0–$0

Materials + rentals, your labor free

Hard

Complex project, structural or code-critical work involved.

Government Data · Government Data · Submitted Quotes (n=0)

How we got these numbers

National benchmark costs from RSMeans, Angi, Fixr, and HomeGuide are adjusted for New Hampshire using two federal datasets: the Bureau of Economic Analysis Regional Price Parity (RPP) index and the Bureau of Labor Statistics (BLS) Occupational Employment and Wage Statistics. New Hampshire's RPP is 1.0 (national baseline = 100) and its BLS labor adjustment factor is 1.05. Higher RPP means goods and services cost more relative to the national average; the BLS factor scales contractor labor rates to local wage levels. We blend these two adjustments, weighted 40% RPP, 60% BLS labor, to produce the ranges shown above.

adjusted_cost = national_benchmark × (0.4 × RPP/100 + 0.6 × bls_labor_adj)

RPP(New Hampshire) = 1.0 · BLS adj = 1.05

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What's included

Item	Qty	Unit Cost	Subtotal
Septic tank	1	$1,500	$1,500
Drain field pipe and stone	1 system	$2,500	$2,500
Distribution box and fittings	1 set	$400	$400
Permit, perc test, and design	1 set	$1,200	$1,200
Materials Total			$5,600

Tools you'll need

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TOOLS YOU PROBABLY OWN

TOOLS TO RENT OR BUY

Licensed septic installer (required)
Design and install must be permitted and inspected
Excavator and heavy equipment
Part of the professional install
Soil/perc testing by a pro
Required before a system is designed

Build sequence

1
A perc test and soil evaluation determine what system the site can support.
COMMON MISTAKE
Sizing or siting a system without proper soil testing fails inspection.
2
An engineer or installer designs the system and pulls health-department permits.
3
The tank is set and the drain field is excavated and built to the approved design.
COMMON MISTAKE
DIY work here is illegal in nearly all areas and risks contaminating groundwater.
4
The distribution box and field lines are laid level for even effluent flow.
5
The health inspector approves the system before it is backfilled and used.

Permits and code requirements

PERMIT REQUIREMENTS

Permit rules for septic system installation vary by city and county in New Hampshire. Most structural, electrical, plumbing, or mechanical work needs a permit and an inspection. Confirm with your local building department, or see the New Hampshire guide for specifics.

PERMIT THRESHOLD

Varies by municipality

Disclaimer: Always verify permit requirements with your local building department before starting work. Requirements vary by municipality and are updated periodically.

Frequently asked questions

NEXT STEPS

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UPDATED JUNE 2026