New Hampshire Septic & Well Water Rules

The NH Department of Environmental Services (NHDES) Subsurface Systems Bureau approves septic system designs and inspects new systems.

This is a short state page. It covers only the facts we've verified from official sources so far.

Septic approvals

• Under Env-Wq 1000, no one may build a structure that discharges wastewater, or build a septic system, without NHDES approval of the plans.
• Plans must be prepared and sealed by an NHDES-permitted designer. Systems must be built by a permitted installer, except homeowners installing for their own primary home.
• You need both an Approval for Construction and an Approval for Operation, issued after an NHDES inspection, before using a new system.
• Approval for Construction is also needed before converting a seasonal home to year-round use, increasing the load on an existing system, or certain additions.

Private well testing

• NHDES recommends testing bacteria and nitrate/nitrite every year, and arsenic and other standard contaminants every 3-5 years. Its guidance also includes PFAS.

Frequently asked questions

Sources

• NHDES: Septic Systems
• NHDES: Septic Designer and Installer
• Env-Wq 1000 rules
• NHDES: Water Testing Guidance for Private Well Users

Last checked: October 21, 2026