DIY Septic System Installation: A Comprehensive Guide
Installing a septic system is a significant undertaking, typically best left to licensed professionals. However, understanding the process can be beneficial, especially if you’re considering purchasing property that requires a septic system or need to oversee a contractor’s work. In some jurisdictions, homeowners are permitted to install their own septic systems, provided they adhere to strict regulations and obtain the necessary permits. This comprehensive guide outlines the steps involved in installing a septic system, but remember to **always check local regulations and obtain necessary permits before starting any work**. This guide is for informational purposes only and should not be considered a substitute for professional advice.
**Disclaimer:** *This guide provides general information and should not be considered a substitute for professional advice. Installing a septic system is a complex and potentially hazardous task. Always consult with licensed professionals and obtain all necessary permits before beginning any work. Failure to comply with local regulations and safety standards can result in fines, property damage, and health risks.*
## I. Initial Considerations and Planning
Before you even think about digging, several crucial steps must be taken to ensure your septic system installation is successful and compliant with local regulations.
**A. Site Evaluation and Soil Testing (Percolation Test):**
* **The Percolation Test (Perc Test):** This is arguably the most critical step. A perc test determines the soil’s ability to absorb water, which is essential for proper wastewater treatment. The test involves digging a series of holes in the proposed drain field area and measuring how quickly water drains from these holes. The results of the perc test will dictate the size and type of septic system required.
* **Procedure:**
1. Dig several test holes (typically 6-12 inches in diameter) to the depth of the proposed drain field (usually 2-3 feet). The number of holes and their spacing will depend on local regulations and the size of the proposed drain field.
2. Pre-soak the holes by filling them with water at least 24 hours before the test. This saturates the soil and provides a more accurate reading.
3. On the day of the test, fill each hole with water to a specific level (e.g., 6 inches from the top).
4. Measure the time it takes for the water level to drop a specific distance (e.g., 1 inch). Record this time for each hole.
5. Calculate the percolation rate by dividing the time (in minutes) by the distance the water dropped (in inches). This will give you the minutes per inch (MPI).
* **Interpreting the Results:**
* Local regulations will specify the acceptable MPI range. If the soil percolates too quickly (e.g., sandy soil), wastewater may not be adequately treated before reaching groundwater. If the soil percolates too slowly (e.g., clay soil), wastewater may back up into the system.
* If the perc test fails (i.e., the percolation rate is outside the acceptable range), alternative septic system designs, such as mound systems or aerobic treatment systems, may be required.
* **Soil Composition Analysis:** A comprehensive soil analysis goes beyond the perc test and identifies the types of soil present (e.g., sand, silt, clay), their proportions, and their nutrient content. This information helps determine the best type of septic system for the site and can inform the design of the drain field.
* **Professional Assistance:** While you can perform a perc test yourself, it’s highly recommended to hire a qualified soil scientist or engineer. They have the expertise to accurately assess the site conditions, interpret the results, and recommend the appropriate septic system design.
**B. Determine Septic System Type and Size:**
* **Conventional Septic System:** The most common type, consisting of a septic tank and a drain field (also called a leach field). Wastewater flows from the house to the septic tank, where solids settle to the bottom (forming sludge) and lighter materials float to the top (forming scum). The partially treated wastewater (effluent) then flows to the drain field, where it is filtered by the soil.
* **Alternative Septic Systems:** Used when conventional systems are not suitable due to poor soil conditions, high water tables, or small lot sizes. Examples include:
* **Mound Systems:** Elevate the drain field above the natural ground level, using a layer of engineered fill to improve drainage.
* **Aerobic Treatment Systems (ATS):** Use air to enhance the treatment process in the septic tank, producing a higher quality effluent.
* **Drip Irrigation Systems:** Distribute effluent through a network of underground drip lines, providing slow and even distribution of wastewater.
* **Constructed Wetlands:** Use plants and microbes to filter wastewater.
* **System Size:** The size of the septic tank and drain field depends on the number of bedrooms in the house and the estimated daily wastewater flow. Local regulations will specify the minimum tank size and drain field area required.
* **Estimating Wastewater Flow:** A general rule of thumb is to estimate 75-100 gallons of wastewater per bedroom per day. For example, a 3-bedroom house would be expected to generate 225-300 gallons of wastewater per day.
**C. Obtain Necessary Permits:**
* **Contact Local Health Department or Permitting Agency:** Before starting any work, contact your local health department or permitting agency to obtain the necessary permits. They will provide you with the specific requirements for septic system installation in your area.
* **Permit Application:** The permit application will typically require detailed information about the site, the proposed septic system design, and the installer (if you’re hiring a contractor). You may also need to submit a site plan, soil test results, and engineering drawings.
* **Inspection Requirements:** The permitting agency will likely require inspections at various stages of the installation process to ensure compliance with regulations. These inspections may include:
* **Pre-Construction Inspection:** To verify the site conditions and the proposed system layout.
* **Tank Installation Inspection:** To ensure the tank is properly installed and sealed.
* **Drain Field Installation Inspection:** To verify the drain field is constructed according to the approved design.
* **Final Inspection:** To confirm the entire system is functioning properly.
**D. System Design:**
* **Professional Design:** It is strongly recommended that a qualified engineer or septic system designer create a detailed design for your septic system. The design will specify the location of the tank and drain field, the size and type of materials to be used, and the installation procedures.
* **Design Considerations:** The design should take into account the site’s soil conditions, topography, setbacks from property lines and water sources, and the estimated wastewater flow.
## II. Preparing the Site
Once you have the necessary permits and a detailed design, you can begin preparing the site for the septic system installation.
**A. Marking the System Location:**
* **Accurate Layout:** Use the approved site plan to accurately mark the locations of the septic tank and drain field. Use stakes, flags, or paint to clearly delineate the boundaries of the excavation areas.
* **Utility Location:** Before digging, contact your local utility companies to locate any underground utilities (e.g., water lines, gas lines, electric cables). This is crucial to avoid damaging these utilities during excavation.
**B. Excavation:**
* **Safety Precautions:** Excavation can be dangerous. Always wear appropriate safety gear, including a hard hat, safety glasses, and steel-toed boots. Ensure the excavation site is properly shored to prevent cave-ins.
* **Equipment:** You will need an excavator, backhoe, or other heavy equipment to dig the holes for the septic tank and drain field. Consider renting equipment if you don’t own it.
* **Septic Tank Excavation:** Dig the hole for the septic tank according to the dimensions specified in the design. The hole should be deep enough to allow the tank to be buried with the top of the tank slightly below ground level. Ensure the bottom of the hole is level and compacted to provide a stable base for the tank.
* **Drain Field Excavation:** Dig the trenches for the drain field laterals according to the design. The trenches should be the correct width and depth, and the bottom of the trenches should be level and free of debris. The spacing between the trenches should also be as specified in the design.
**C. Material Delivery and Storage:**
* **Schedule Deliveries:** Coordinate the delivery of the septic tank, drain field materials (e.g., gravel, pipes, geotextile fabric), and other supplies. Ensure you have adequate space to store these materials on-site.
* **Protect Materials:** Protect the materials from damage and contamination. Store the septic tank on a level surface and cover it to prevent debris from entering. Store the drain field materials in a clean and dry place.
## III. Septic Tank Installation
The septic tank is the heart of the system, where initial wastewater treatment occurs.
**A. Preparing the Tank Bed:**
* **Level Base:** Ensure the bottom of the excavated hole for the septic tank is level and compacted. This is crucial to prevent the tank from settling unevenly, which could damage the tank or the connecting pipes.
* **Gravel Bed (Optional):** Some installers recommend placing a layer of gravel (e.g., 4-6 inches) at the bottom of the hole to provide additional drainage and support for the tank. Check with your local regulations to see if this is required.
**B. Setting the Tank:**
* **Safe Handling:** Septic tanks are heavy and require specialized equipment to move and position. Use a crane, excavator, or other appropriate lifting device to carefully lower the tank into the hole. **Never attempt to lift or move a septic tank manually.**
* **Proper Orientation:** Ensure the tank is oriented correctly, with the inlet pipe facing the house and the outlet pipe facing the drain field. The tank should also be level in both directions.
**C. Connecting Inlet and Outlet Pipes:**
* **Watertight Connections:** Connect the inlet pipe from the house to the septic tank and the outlet pipe from the tank to the drain field. Use appropriate fittings and sealant to ensure watertight connections. This is essential to prevent leaks and groundwater contamination.
* **Slope:** Ensure the inlet and outlet pipes have a slight downward slope (e.g., 1/4 inch per foot) to allow wastewater to flow freely.
* **Inlet Baffle:** The inlet pipe should have a baffle or tee fitting inside the tank to prevent solids from flowing directly into the drain field. The baffle helps to distribute the flow and promote settling of solids.
* **Outlet Filter:** Install an effluent filter on the outlet pipe to prevent solids from entering the drain field. The filter should be easily accessible for cleaning.
**D. Backfilling Around the Tank:**
* **Proper Material:** Use a suitable backfill material (e.g., sand or gravel) to fill the space around the septic tank. Avoid using large rocks or sharp objects that could damage the tank.
* **Compaction:** Compact the backfill material in layers to prevent settling. Use a hand tamper or plate compactor to ensure the backfill is properly compacted.
* **Avoid Over-Compaction:** Be careful not to over-compact the backfill, as this could damage the tank. Compact the backfill evenly around the tank.
## IV. Drain Field Installation
The drain field is where the final treatment of wastewater occurs as it filters through the soil.
**A. Preparing the Trenches:**
* **Level Bottom:** Ensure the bottom of the drain field trenches are level and free of debris. This is crucial for even distribution of wastewater throughout the drain field.
* **Gravel Bed:** Place a layer of gravel (typically 6-12 inches) at the bottom of the trenches. The gravel provides drainage and support for the drain field pipes. Use washed gravel that is free of fines (small particles).
**B. Laying the Drain Field Pipes:**
* **Perforated Pipes:** Use perforated pipes specifically designed for drain fields. The perforations allow the wastewater to seep out into the surrounding gravel and soil.
* **Proper Spacing:** Space the pipes evenly in the trenches according to the design. The spacing is important for ensuring even distribution of wastewater and preventing overloading of the soil.
* **Slope (Optional):** Some drain field designs call for a slight slope in the pipes to promote drainage. Check with your local regulations and the system design to see if this is required.
**C. Covering the Pipes with Gravel:**
* **Gravel Coverage:** Cover the drain field pipes with gravel to a depth of several inches. The gravel helps to protect the pipes from damage and provides additional drainage.
* **Geotextile Fabric:** Place a layer of geotextile fabric over the gravel to prevent soil from clogging the gravel and pipes. The fabric should be porous enough to allow water to pass through but prevent soil particles from entering.
**D. Backfilling the Trenches:**
* **Suitable Material:** Use a suitable backfill material (e.g., topsoil) to fill the trenches. Avoid using large rocks or sharp objects that could damage the pipes.
* **Compaction:** Compact the backfill material in layers to prevent settling. Avoid over-compacting the backfill, as this could reduce the soil’s ability to absorb water.
**E. Distribution Box (D-Box):**
* **Purpose:** A distribution box is used to evenly distribute wastewater to multiple drain field laterals. It is typically installed between the septic tank and the drain field.
* **Level Installation:** The D-box must be installed level to ensure even distribution of wastewater. Use a level to check the D-box and adjust it as needed.
* **Outlet Connections:** Connect the outlet pipes from the D-box to the drain field laterals. Ensure the connections are watertight.
## V. Connecting the System to the House
This involves connecting the house’s plumbing to the septic tank.
**A. Locating the Sewer Line:**
* **Trace the Line:** Locate the sewer line that exits the house and connects to the municipal sewer system (if applicable). If there is no existing sewer line, you will need to install one.
**B. Connecting to the Septic Tank:**
* **Cut and Cap (if applicable):** If connecting to an existing sewer line, cut and cap the line at a point before it connects to the municipal sewer system. Ensure the cap is watertight.
* **Connect to Inlet Pipe:** Connect the house’s sewer line to the inlet pipe of the septic tank. Use appropriate fittings and sealant to ensure a watertight connection.
* **Slope:** Ensure the sewer line has a slight downward slope (e.g., 1/4 inch per foot) to allow wastewater to flow freely to the septic tank.
**C. Testing the Connection:**
* **Water Test:** After connecting the sewer line to the septic tank, run water from the house to test the connection for leaks. Check the connections at the septic tank and the sewer line for any signs of leaks.
## VI. Final Steps and System Startup
These final steps are crucial for ensuring the system functions correctly and is properly documented.
**A. Final Inspection:**
* **Schedule Inspection:** Schedule a final inspection with your local health department or permitting agency. They will inspect the entire system to ensure it is installed correctly and complies with regulations.
* **Address Deficiencies:** If the inspector identifies any deficiencies, address them promptly and schedule a re-inspection.
**B. Backfilling and Grading:**
* **Complete Backfilling:** Complete the backfilling around the septic tank and drain field. Ensure the backfill is properly compacted.
* **Grading:** Grade the area around the septic tank and drain field to promote drainage away from the system. This will help to prevent water from pooling on top of the system.
**C. Seeding and Landscaping:**
* **Vegetation:** Seed the area above the drain field with grass or other shallow-rooted vegetation. Avoid planting trees or shrubs with deep roots, as they could damage the drain field pipes.
* **Avoid Impermeable Surfaces:** Do not cover the drain field with impermeable surfaces, such as concrete or asphalt. This will prevent water from evaporating and could overload the system.
**D. System Startup:**
* **Initial Water Use:** After the final inspection and backfilling are complete, you can begin using the septic system. Start with moderate water use to allow the system to adjust.
* **Avoid Overloading:** Avoid overloading the system with excessive water use, especially in the first few weeks. Spread out laundry loads and avoid taking long showers.
**E. Record Keeping:**
* **Keep Records:** Keep detailed records of the septic system installation, including the system design, permit information, inspection reports, and as-built drawings. This information will be useful for future maintenance and repairs.
## VII. Septic System Maintenance
Proper maintenance is essential for ensuring the long-term performance of your septic system.
**A. Regular Pumping:**
* **Frequency:** Have the septic tank pumped regularly, typically every 3-5 years, depending on the size of the tank and the number of people in the household.
* **Professional Pumping:** Hire a licensed septic tank pumper to pump the tank. They will properly dispose of the sludge and scum that accumulate in the tank.
**B. Water Conservation:**
* **Reduce Water Use:** Conserve water to reduce the amount of wastewater that enters the septic system. Fix leaky faucets and toilets, and use water-efficient appliances.
**C. Proper Waste Disposal:**
* **Avoid Flushing Inappropriate Items:** Avoid flushing inappropriate items down the toilet, such as diapers, feminine hygiene products, paper towels, and grease. These items can clog the septic tank and drain field.
**D. Drain Field Protection:**
* **Avoid Driving or Parking on Drain Field:** Avoid driving or parking vehicles on the drain field, as this can compact the soil and damage the pipes.
* **Divert Runoff:** Divert rainwater runoff away from the drain field to prevent it from becoming waterlogged.
**E. Regular Inspections:**
* **Professional Inspections:** Have the septic system inspected by a qualified professional every few years to identify any potential problems early on.
## VIII. Troubleshooting Common Problems
Even with proper maintenance, septic systems can experience problems. Here are some common issues and potential solutions:
**A. Slow Drains:**
* **Cause:** Clogged pipes, full septic tank, or drain field problems.
* **Solution:** Check for clogged pipes and clear them. Have the septic tank pumped. If the problem persists, have the drain field inspected.
**B. Sewage Backup:**
* **Cause:** Clogged sewer line, full septic tank, or drain field failure.
* **Solution:** Check for clogged sewer line and clear it. Have the septic tank pumped. If the problem persists, the drain field may need to be repaired or replaced.
**C. Foul Odors:**
* **Cause:** Leaking septic tank, clogged vent pipe, or drain field problems.
* **Solution:** Check for leaks in the septic tank. Check the vent pipe for obstructions. If the odor persists, have the drain field inspected.
**D. Standing Water in Drain Field:**
* **Cause:** Drain field failure due to overloading or clogging.
* **Solution:** Reduce water use. Have the drain field inspected and repaired or replaced.
## IX. Safety Considerations
Safety should be a top priority when working with septic systems.
**A. Confined Space Hazards:**
* **Septic tanks are confined spaces:** They can contain dangerous gases, such as methane and hydrogen sulfide. Never enter a septic tank without proper training and equipment.
**B. Excavation Hazards:**
* **Trench collapse:** Excavations can collapse, burying workers. Always shore up trenches to prevent collapse.
* **Underground utilities:** Digging can damage underground utilities, such as gas lines and electric cables. Always call before you dig.
**C. Biohazards:**
* **Wastewater contains bacteria and viruses:** Always wear protective clothing and gloves when working with wastewater. Wash your hands thoroughly after working with wastewater.
**D. Heavy Equipment:**
* **Operating heavy equipment can be dangerous:** Only operate equipment that you are trained to use. Follow all safety precautions.
## X. Conclusion
Installing a septic system is a complex project that requires careful planning, execution, and adherence to local regulations. While it’s possible for homeowners to install their own systems in some areas, it’s often best to hire a qualified professional. Understanding the installation process can help you make informed decisions and ensure that your septic system is properly installed and maintained for years to come. Remember to always prioritize safety and consult with local authorities before beginning any work.
This detailed guide aims to provide a thorough understanding of the septic system installation process. However, laws and regulations vary greatly depending on the municipality, state and even county. Furthermore, only a qualified professional can determine the specific requirements for your property and situation. Please consult with the relevant authorities and licensed professionals before undertaking this project.