Building a septic tank requires a permit, a soil test, and a licensed contractor in most places
You cannot legally build a septic tank yourself in nearly every U.S. state and county. The system must be designed by a licensed engineer or septic professional, installed by a licensed contractor, and inspected by your local health department before you can use it. Septic systems handle human waste and groundwater contamination is a serious public health risk, which is why the rules are strict.
What you can do is understand the process, hire the right people, and know what to expect at each step. This guide walks through the real sequence: getting a permit, having your soil tested, choosing a system design, hiring a contractor, and passing inspection.
Key Takeaways
- Your local health department or county environmental office issues the permit and sets the rules for your specific property.
- A soil percolation test determines how fast water drains through your soil, which controls tank size and drain field design.
- Licensed septic designers and contractors are required by law; hiring unlicensed workers voids your permit and creates liability.
- The entire process from permit to final inspection typically takes two to four months, depending on soil conditions and inspection schedules.
- System cost varies widely by location and soil type, but budget for several thousand dollars and expect the contractor to give you a written estimate before work starts.
Step 1: Contact your local health department and get a permit process
Start by calling your county health department, environmental health office, or building department—the name varies by location. Ask for the septic system permit process and the design standards for your county. Some counties have their own rules; others follow state guidelines. The office will tell you which documents you need to submit.
You will typically need a property survey showing lot lines and the location of your house, well (if you have one), property lines, and any wetlands or water bodies. You may also need proof of ownership and a site plan drawn to scale. Ask the health department whether you can submit the process yourself or whether a licensed designer must do it.
Do not start any work before the permit is issued. Working without a permit can result in fines, a requirement to remove the system, and difficulty selling the property later.
Step 2: Have a soil percolation test performed
A percolation test (or "perc test") measures how fast water drains through your soil. The health department will specify how many test holes to dig, how deep, and the exact procedure. This test determines the size of your drain field and whether a standard system will work on your property.
You can hire a licensed septic designer or soil scientist to perform the test, or in some counties a contractor can do it. The test involves digging holes, filling them with water, and measuring how much the water level drops over a set time period. Results are recorded on an official form and submitted with your permit process.
If your soil drains too slowly, you may need a larger drain field, a mound system, or an engineered alternative like a sand filter. If it drains too fast (sandy soil), you may need additional treatment. Poor results do not mean you cannot build a system—it means the design will be different and possibly more expensive.
Step 3: Work with a licensed septic designer to create system plans
A licensed septic designer or engineer will use your soil test results, lot size, and household size to design a system that meets your county's standards. The designer creates a detailed plan showing the tank location, drain field layout, pipe sizes, and any special components. This plan is submitted with your permit process.
The designer must be licensed in your state. Licensing requirements vary—some states require a professional engineer license, others have a separate septic designer license. Your health department can tell you what credentials are required in your area and can provide a list of licensed designers.
The design plan is not something you create yourself. It is a technical document that must meet specific engineering standards and local codes. The designer is responsible for its accuracy, and the health department will review it before approving your permit.
Step 4: Hire a licensed septic contractor to install the system
Once your permit is approved, you hire a licensed septic contractor to build the system according to the approved plans. The contractor orders the tank (usually concrete, fiberglass, or plastic), excavates the drain field, lays pipe, and installs any additional components like distribution boxes or pumps.
Get written estimates from at least two contractors. The estimate should list the tank size, materials, labor, and any site-specific costs (like rock or sand if your soil needs amendment). Ask whether the estimate includes the final inspection fee and any required maintenance visits after installation.
Check that the contractor holds a current license in your state. You can verify this through your state's licensing board or health department. Do not hire unlicensed workers—if the system fails or causes contamination, you are liable, and your homeowner's insurance may not cover it.
Step 5: Prepare the site and monitor installation
Before the contractor arrives, mark the approved tank and drain field locations on your property. The contractor will need clear access to dig. Remove or protect any structures, utilities, or landscaping in the work area. Call your local utility locating service (usually 811 in the U.S.) to mark underground gas, electric, and water lines before any digging begins.
The contractor will excavate the tank hole and drain field trenches, set the tank, connect inlet and outlet pipes, and backfill. The process typically takes three to five days depending on soil conditions and system size. You do not need to be present every moment, but it is reasonable to check in and ask the contractor to show you the tank location and drain field layout.
Keep the approved plans and any site modifications documented. If the contractor needs to move the tank or drain field because of unexpected soil or rock, the health department must approve the change before work continues.
Step 6: Schedule and pass the final health department inspection
Once the tank is installed and pipes are connected but before the system is covered with soil, the contractor notifies the health department for a rough inspection. The inspector checks that the tank is the correct size, pipes are properly sloped, and the system matches the approved plans.
If the inspection passes, the contractor backfills the trenches and covers the tank. A final inspection follows to confirm the system is complete and properly covered. Only after the final inspection passes can you legally use the system.
If the inspector finds problems, the contractor must correct them and request a re-inspection. This can add time and cost. Inspections are usually scheduled within one to two weeks, but some counties have longer wait times during busy seasons.
Frequently Asked Questions
Can I install a septic system myself to save money?
No. Your county requires a licensed contractor to install the system, and the health department will not issue a permit for owner-installed work. Installing it yourself voids the permit, creates legal liability if the system fails, and makes the property difficult to sell. The cost of hiring a licensed contractor is a legal requirement, not optional.
How much does a septic system cost?
Cost varies by location, soil type, and system complexity. A standard gravity system in favorable soil might cost $3,000 to $5,000, while a mound system or engineered alternative can cost $8,000 to $15,000 or more. Get written estimates from contractors before committing. Some counties offer cost-share programs for repairs or upgrades; ask your health department.
What if my soil test shows poor drainage?
Poor drainage does not prevent you from building a system—it changes the design. You may need a larger drain field, a mound system (where soil is brought in and built up), a sand filter, or a treatment system. The licensed designer will specify what works for your soil. These alternatives cost more but are legal and effective.
How long does the whole process take?
From permit process to final inspection typically takes two to four months. Soil testing takes one to two weeks, permit review takes two to four weeks, and installation takes one to two weeks. Inspection scheduling depends on your county's workload. Plan ahead if you need the system by a specific date.
Do I need a septic system if I have a well?
Yes. A well supplies drinking water; a septic system treats wastewater. They are separate systems serving different purposes. Your county will require both if you are not connected to municipal water and sewer. The well and septic system must be located far apart to prevent contamination.