09/07/2026
Whether your septic system needs repair, replacement, or an upgrade, or you’re looking to add square footage, a bedroom, or an accessory dwelling unit (ADU), you must submit a permit for any septic system change.
Adding to or repairing any major component of the system, such as the tank(s) or drainfield, requires a permit from the County.
A permit is required for:
- Installing a new system or adding a new tank
- Repairing, replacing, or modifying the drainfield
- Tank repair or replacement
- Connecting a new structure to the existing system or adding a new bedroom to your home (ex: ADU, shop)
A permit is not required, but professional service is recommended for:
- Water-tight tank riser installation
- Replacing a failed sewage pump or alarm panel (like-for-like)
- Fixing a broken transport line and not a drainfield lateral
- Replacing an outlet baffle or the distribution box
- Installing monitoring ports or an effluent filter
One of the easiest ways to protect your investment is to ensure you always choose a licensed septic professional to work on your system. Always contact a licensed septic designer before making a change to your septic system.
To learn about Island County’s septic permitting process, check out our educational brochure: https://www.islandcountywa.gov/DocumentCenter/View/9841/Septic-Permitting-Process?bidId=