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Building a New Septic System
Before Building
Confirm whether a septic system is allowed on your property. If your property is within 200 feet of a public sewer line and service is available, or if it is located within a city utility service area, you may be required to connect to sewer instead of installing a septic system.
Sewer service may be provided by a county, city, or Yakama Nation system. Contact the sewer operator for availability and connection requirements.
How to Apply
If a septic system is allowed on your property, you will need approval from the Health District before designing or building a new system. The steps below guide you through the process from application to installation.
Complete an On-Site Sewage Application and select the option for a Site and Soil Evaluation. This evaluation requires digging test holes in the proposed drain field area so YHD can evaluate the site and soil type and depth to determine whether a system can be installed in a certain location, and what level of treatment is required.
You may dig the test holes on your own or hire a professional. Review the Site and Soil Evaluation guidelines for detailed instructions.
Once the test holes are ready, contact YHD to schedule your evaluation.
After YHD completes the site and soil evaluation, consult with a Licensed Septic System Designer or Professional Engineer. The designer will review the site & soil report , determine the most appropriate system type, and prepare your septic system design plans.
View a list of Licensed Designers and Installers in Yakima County.
Note: Homeowners can design their own conventional/gravity septic system for their primary single-family home. This option does not apply to accessory dwelling units, rental or non–owner-occupied homes, or any other types of septic systems. For more information on designing a conventional system, review the Homeowner’s Design Packet.
After your design is complete, submit the On-Site Sewage Permit Application again and select the option for a new septic system permit depending on the type of system that will be installed.
Your application should include:
- On-site Sewage System Permit Application
- Septic design
- Application fee
Once the application has been submitted, YHD can sign off on the construction permit for your new residence.
Your septic designer will submit the completed system design to YHD for review. YHD staff will check the design for compliance with applicable code requirements. Once approved, YHD will issue your Septic System Permit, allowing installation to begin.
A Licensed Septic System Installer must install the system in accordance with the approved design plans.
After installation, the installer and designer must create an as-built drawing that shows the exact location and layout of the system components. This record must be submitted to YHD for review and added to your permanent property file.
Download the As-Built Drawing Form.
Note: Homeowners can install their own conventional/gravity septic system for their primary single-family home. This option does not apply to accessory dwelling units, rental or non–owner-occupied homes, or any other types of septic systems. For more information on designing a conventional system, review the Homeowner’s Design Packet.
Before the system is covered, YHD will complete a final inspection to verify that the septic system matches the as-built record. Once the final inspection is approved, the system may be covered, and YHD can sign off on a Certificate of Occupancy for your residence.
If the system has any electrical components, YHD will verify that these are functioning properly and that wastewater will be evenly dispersed by the system. The installer must be on site at the time of the inspection for these types of systems.
What Determines the Type of Septic System You Need
The type of system you will need to install will mainly depend on soil depth, soil type, slope, and setbacks (minimum distance to certain site features).
- Soil depth affects what kind of system can be safely installed.
- Soil type affects how large the system must be.
- Slope can limit where and how a system can be placed.
- Setbacks can limit where and how a system can be placed, or impact the kind of system that is required.
Types of Septic Systems
Learn more about different types of systems
A conventional (gravity) septic system can only be used when the property has more than 4 feet of suitable soil and a gentle or moderate slope. This type of system includes a septic tank and a drain field. Wastewater flows from the home into the septic tank, where heavier solids settle at the bottom and lighter materials float to the top. The partially treated water then flows out of the tank and is carried by gravity to the drain field, where the soil filters and cleans it before it reaches groundwater.
Pressurized septic systems are used when a property has only a small amount of native suitable soil, often just two to three feet, and wastewater must be distributed evenly across the drain field. Wastewater flows from the septic tank into a pump chamber, where a pump sends controlled doses of wastewater through the drain field lines.
Some systems use level-based dosing, meaning the pump turns on when the chamber reaches a set level and shuts off after enough wastewater has been distributed. Other systems use timed dosing, where the pump operates on a preset on-and-off schedule. Both methods help spread wastewater evenly and give the soil time to absorb it between doses.
Many systems also include an alarm that activates if the pump fails or the chamber overfills.
Alternative septic systems may be needed on more challenging sites, such as properties with shallow soils or steep slopes. Common types include mound systems, aerobic systems, sand filters, and other advanced treatment systems.
These systems are often more expensive than conventional systems and may require more frequent inspections and maintenance.
Learn more about alternative septic system types.