What to Expect During a Septic System Replacement
TL;DR: Replacing a septic system is a multi-step process that typically involves soil testing, system design, permits, excavation, installation, inspection, and final grading. The entire process can take anywhere from a few days to a few weeks depending on your site conditions, permitting timelines, and system complexity. This guide walks you through the complete septic system replacement process, key steps, and what to expect during each phase—from the first consultation to your final inspection.
If you’re facing a failing septic system, you’re probably wondering what replacing it actually involves. The good news is that while the process is detailed, a qualified team can walk you through each step and ensure everything is handled smoothly.
The septic system replacement process typically includes several stages: evaluation, design, permitting, excavation, installation, inspection, and restoration. Homeowners in southern New Hampshire often have additional considerations such as high water tables, variable soil types, and older property layouts.
Here’s the step-by-step breakdown.
Step 1: Initial Assessment and Consultation
The first step in any septic system replacement is an inspection and evaluation of your existing system. A licensed septic contractor will assess the condition of the tank, drainfield, and surrounding soil. If the system is outdated, leaking, or has failed entirely, they’ll recommend replacement and explain your options. If your sewer lines need to be looked at, they can perform a camera inspection service.
At this point, your contractor will also help you understand what parts of your property will be affected and discuss your goals—whether that’s upgrading capacity, preparing for a home addition, or simply replacing a failing system.
Step 2: Soil Testing and Site Evaluation
Before a new system can be designed, your property’s soil must be evaluated. This usually involves a test pit or perc test, which determines how well your soil absorbs water. In New Hampshire, the New Hampshire Department of Environmental Services (NHDES) requires this step before permitting.
Soil testing results affect system layout, drainfield location, and design requirements. For example, poorly draining soils may require a raised system or additional filtration. Your contractor will document these findings and use them for designing.
Step 3: Septic System Design
A licensed septic designer will use your soil data, household size, and site layout to create a custom plan. This includes:
Septic tank size and location
Drainfield type and dimensions
Pipe layout and elevation
Setback distances from wells, buildings, and property lines
Your system must meet all NHDES regulations and local codes. Once the design is complete, it is submitted to the state for approval. This step can take a few days to a few weeks depending on backlog and complexity.
Step 4: Permitting
Before work begins, you’ll need an approved design and the appropriate permits. In southern New Hampshire, this often includes:
Subsurface system approval (State of NH)
Local health or zoning department approval
Excavation or site disturbance permits (if applicable)
Your septic contractor typically handles this process on your behalf, but the timeline can vary based on your municipality’s review schedule.
Step 5: Excavation and Removal of Old System
Once permits are approved, the physical work begins. The old septic tank and drainfield are excavated and removed. This can be the most disruptive part of the septic system replacement process, particularly if your existing tank is in poor condition or deeply buried.
During excavation, your contractor will take precautions to minimize damage to surrounding areas. Driveways, trees, gardens, or fences near the system may be affected depending on your site layout. Temporary fencing or matting can be used to protect vulnerable areas.
Step 6: Installing the New Septic System
With the site cleared and prepped, the new system is installed according to the approved design. This typically includes:
Placing and leveling the septic tank
Installing the distribution box and connecting lines
Constructing or restoring the drainfield
Backfilling and grading the area
Tank materials (concrete, plastic, or fiberglass) and drainfield types (stone and pipe, chamber, or advanced treatment units) vary based on your soil and site needs.
Proper septic system installation is critical for long-term performance. Your contractor will check elevations, test for leaks, and ensure all components meet code.
Step 7: Final Inspection and System Approval
After installation, your local or state inspector will visit the site to confirm everything matches the approved design and is functioning properly. This includes:
Checking tank placement and elevation
Verifying pipe slope and connections
Ensuring proper drainfield construction
Confirming setback and spacing requirements
Once the system passes inspection, you’ll receive formal approval and the system can be put into operation.
Step 8: Restoration and Cleanup
After approval, your contractor will complete final grading and site restoration. This may include reseeding grass, re-graveling driveways, or replacing landscaping. While full restoration may take a few weeks depending on weather and growing conditions, your contractor should leave the site safe, clean, and functional.
How Long Does Septic Replacement Take?
One of the most common questions homeowners ask is: how long does septic replacement take? The answer depends on permitting timelines, soil conditions, and system complexity. On average:
Soil testing and design: 1–2 weeks
Permitting: 1–3 weeks
Excavation and installation: 2–5 days
Inspection and restoration: 2–5 days
From start to finish, the septic system installation timeline may range from 3 to 6 weeks. Delays are possible if weather is poor, permitting is slow, or unexpected issues arise during excavation.
What Homeowners Should Expect During the Process
Some disruption to yard and landscape
Noise and excavation equipment on-site for several days
Limited or no access to plumbing during critical stages
Coordination with utility marking and inspection schedules
A good contractor will keep you informed every step of the way and minimize downtime where possible.
Why Working with the Right Contractor Matters
Septic system replacement is an investment in your home’s long-term health and value. Choosing the right contractor means hiring a partner who understands how to design a system that complies with New Hampshire regulations, uses the right materials for your soil and property conditions, and communicates clearly about cost and timelines. A reputable contractor will also take care to protect your property throughout the process, minimizing disruption and leaving your yard as intact as possible when the work is done.
Townes Septic has decades of experience replacing systems across southern New Hampshire. From start to finish, we prioritize professionalism, education, and clean execution.
Get Help with Your Septic Tank Replacement Process
If you think your system is reaching the end of its lifespan, or you’re already facing failure, don’t wait for it to become a crisis. Reach out to Townes Septic to learn more about the septic system replacement process and what the next steps look like for your property.
We’re here to guide you from inspection and design to the final approval.