ADU Sewer Line Connection

When you’re building an ADU, making sure your sewer line connection is done right is key to avoiding future problems. At Modern ADU Builder, we specialize in handling the sewer connections for your ADU with care and precision. We provide a complete service that ensures your accessory dwelling unit is properly connected to the sewer system, meeting all local codes and standards.


We know sewer connections can be confusing and stressful for homeowners. That’s why we take the time to guide you through every step, from assessing your site to completing the final hookup. Our expertise means you won’t have to worry about permits, inspections, or unexpected costs related to your sewer line.


Choosing the right company for your ADU sewer connection saves you time and hassle. We focus on clean, efficient installation so your new unit functions smoothly and complies with all regulations. When you work with us, you get a team that understands what your project needs to succeed.

Installation Process

We focus on making sure your ADU sewer line is installed correctly, safely, and up to code.

  • 1. Initial Consultation and Site Assessment

    We start by visiting your property to inspect the location where the ADU sewer connection will be installed. This helps us identify the best route to the city sewer or septic system.


    During this visit, we check for any obstacles like large tree roots, existing pipes, or uneven ground that could affect the installation. We also look at the slope of your yard because sewer lines need to flow downhill properly.


    We then discuss your needs, local code requirements, and permits that may be needed. This initial step ensures every detail is in place before work begins, avoiding costly surprises later.

  • 2. Detailed Project Planning and Timeline

    Once the site assessment is complete, we create a detailed plan that includes cost estimates, materials needed, and the exact steps for the connection.


    We schedule each phase, including permit submissions, excavation, pipe installation, and final inspections. This timeline helps you understand when work will start and finish.


    We keep in contact throughout the project to update you on progress and quickly handle any issues. Our planning makes sure you get a smooth, timely sewer connection for your ADU with no missed steps.

  • 3. Trenching and Pipe Laying Techniques

    First, we dig a trench deep enough to meet local code requirements, often 18 to 24 inches below the surface. This ensures proper slope for sewer flow and prevents damage from surface weight or freezing.


    We use durable PVC pipes designed for sewer use. Pipes are laid with a slight downward slope, usually 1/4 inch per foot, to help waste flow by gravity. Joints are sealed tightly to avoid leaks.


    Backfilling is done with clean soil and compacted carefully to avoid pipe movement. We also mark the trench location for future access and repair needs.

  • 4. Inspection and Testing Procedures

    After pipe installation, we perform pressure testing or water testing. This checks for leaks or blockages before covering the trench.


    We schedule inspections with your city’s building department to verify all work follows local rules. Documentation is prepared to confirm compliance.


    Our team fixes any issues found during tests or inspections, so your system is reliable and ready for use.

  • 5. Final Connection and System Integration

    We connect the new sewer line to your main sewer or septic system, making sure the link is secure and leak-proof. This may involve accessing the city sewer cleanout or your property’s main sewer line.


    You’ll receive guidance on maintaining your new connection to avoid clogs or damage. We also clean up the work area and remove excess materials.


    Integration ensures your ADU’s wastewater safely flows away from your home without risking backups or odor problems.

Sewer Line Connection Services

Site Inspection and Planning

We start by inspecting your property and locating the existing sewer line. This helps us plan the best route for your ADU connection. We consider property layout, slope, and distance. This step ensures the connection meets city rules and functions well.


Our planning aims to avoid future problems with sewer flow. You will get a clear plan before we start digging. This service saves you time and money. We identify potential obstacles early. Communication is key, so we keep you informed.

Trenching and Excavation

We use the right equipment to minimize disruption. The trench is dug to the proper depth for your area’s sewer system. We carefully handle landscaping and driveways during excavation.


We protect your property while working efficiently. We remove dirt and debris to keep the site clean. Our crew checks for underground utilities first to avoid damage. This step sets the foundation for a strong sewer connection. You can expect quick, professional service.

Site Restoration and Cleanup

 Our team replaces any damaged landscaping or hardscape when possible. We remove all debris and construction materials. We make sure your yard or driveway looks neat again.



You can trust us to respect your home environment. We finish with a thorough cleanup to avoid future problems. Our goal is a smooth end to the sewer connection work. You’ll get a clean, functional site ready for use.

Permitting and Inspections

We manage applying for sewer connection permits on your behalf. Our team submits all required documents to local agencies. We schedule inspections and coordinate with city officials.


We fix any issues the inspectors may find. We keep you updated on the permit status throughout the process. You won’t need to worry about missing deadlines or requirements. Our experience helps the approval go smoothly. We aim to make compliance simple and clear for you. Getting proper permits avoids costly delays in your project.

FAQs on ADU Sewer Line Connection

Hi there! Have some questions about our service? Find the answers below. 

  • What are the requirements for connecting an ADU to the existing sewer line?

    The requirements include adequate slope (typically 1/4 inch per foot) for proper drainage. A cleanout must be installed within 2 feet of the ADU and at any junction or bend exceeding 45 degrees. The connection must comply with local plumbing codes regarding pipe materials, typically requiring schedule 40 PVC. Most jurisdictions require backwater valves if the ADU connection is below the upstream manhole cover. The connection point to the main sewer line typically requires inspection by local authorities before backfilling.

  • How much does it typically cost to install the sewer line for an ADU?

    Sewer line installation for an ADU typically costs between $3,000 and $10,000. Factors affecting cost include distance from the main line, excavation difficulties, and local labor rates. Connection fees charged by municipalities typically range from $1,000 to $5,000 depending on location. Additional costs may include permits ($200-$500) and possible system development charges ($2,000-$8,000). Complex installations requiring pumps or significant grading can increase costs to $15,000 or more.

  • What is the process of obtaining permits for sewer line connections for an ADU?

    You need to submit application forms to your city’s building or public works department. After review and fee payment, inspections are scheduled during and after installation to approve the work.

  • How long does it take to complete a sewer line hookup for a new ADU?

    The physical installation typically takes 2-5 days depending on complexity and length. Permit processing can take 2-8 weeks depending on the municipality's backlog. Inspection scheduling may add 1-2 weeks to the timeline. Weather delays and unexpected underground obstacles can extend the timeline. The entire process from initial application to completed connection typically takes 6-12 weeks.

  • Can an ADU share a sewer line with the main house, and what are the implications?

    Yes, sharing is common but you must ensure the line can handle the extra load. Sometimes, upgrades to the existing line are needed to prevent backups or damage.