
It Looked Like an Easy ADU. It Wasn’t.
A family owned three and a half acres inside City of Bend. Existing home, existing septic, mountain views, and room to add. They had plans drawn for an 800-square-foot, one-bedroom ADU and the project looked straightforward on paper. A pre-purchase SiteFacts report came back before any further money moved. The sewer situation ended the ADU. City of Bend Code Chapter 15.10 (General Sewer Regulations) governs sewer connection requirements within city limits. For ADU construction specifically, the code allows exactly two options: the ADU connects to the existing on-site septic system if that system can support the increased load, or the ADU connects to city sewer. Those are the only two paths. There’s no third option, no variance process, and no engineering workaround that changes this. In the case described above, the existing septic system could not support an additional dwelling unit. The nearest city sewer connection was more than a quarter mile from the property. Three separate sources, including City of Bend Engineering, Deschutes County’s onsite wastewater division, and a licensed septic consultant retained specifically to find an alternative, all confirmed the same conclusion: there was no compliant path for the ADU. The connection cost at that distance made the project economically impossible. The ADU was abandoned. The owners built a shop instead. This is an edge case. Not every ADU project inside City of Bend runs into this. But edge cases are where the actual rules surface, and what this one reveals matters: ADU feasibility depends on more than zoning permission. The constraints that quietly end projects are usually the things no one thought to check before purchase — jurisdiction, sewer service, septic capacity, utility distance, overlays, access, and permit triggers. The sewer question here is one example of how that pattern shows up in the field. Why City Limits and County Land Look the Same on the Ground The boundary that matters for sewer requirements is not the property line, the lot size, or what the property looks like from the road. It is the jurisdictional boundary. Large parcels inside City of Bend are subject to city code even when they feel rural, even when they border county land, and even when the surrounding area operates on septic. City limits run where they run. Properties inside city limits answer to the city’s code, not to Deschutes County. This is the piece most buyers don’t check before they purchase. Most people planning an ADU don’t start with an architect. They go straight to a builder. And a builder’s job starts at the build phase, not the due diligence phase. Nobody in that sequence is flagging the jurisdictional boundary before the design budget is committed. The assumption, understandable but wrong, is that a property this large and this rural in character must be on county rules. In Central Oregon, that assumption ends projects. In the case this post describes, the property owner initially contacted Deschutes County’s onsite wastewater division to explore adding capacity to the existing system. The county’s response was direct: “Due to City of Bend’s code, the county cannot approve any new or alterations to existing systems.” The county had no authority to act because the property was inside city limits, and the city’s code controlled entirely. The Two-Option Framework Under Chapter 15.10 City of Bend Code Chapter 15.10 establishes a clear requirement for ADUs within city limits, and it does not leave room for interpretation. If the existing on-site septic system can support the increased load from an ADU, the ADU may connect to that system. If the existing system cannot support the load, connection to city sewer is required. A new, separate septic system for the ADU is not permitted under this code. This is the direct answer to the question most buyers and builders do not think to ask before purchase: does City of Bend require sewer connection for ADUs? If the existing septic cannot support the additional unit, yes. Connection to city sewer is required regardless of how far away the nearest connection happens to be. City of Bend Engineering confirmed this position in writing: “if your current tank is not feasible to serve the ADU addition, connection to city sewer is required.” The county confirmed from their side: “The City won’t allow upgrades to an existing system to serve an ADU.” Two agencies, one answer. When the Sewer Is a Quarter Mile Away The economic problem in situations like this is not regulatory. It is geographic. A sewer extension of more than a quarter mile carries a construction cost that no ADU rental income can justify. The numbers don’t work. And no amount of project management, phasing, or negotiation changes them. The sewer is where it is. In the case this post describes, a licensed septic consultant was retained specifically to find a compliant engineering path around the code. His conclusion, after reviewing the site and the applicable code: no compliant path existed for the ADU. It was not a close call. That is what Chapter 15.10 does in practice on lots where the sewer is far away. It does not just raise costs. It ends projects. The Land Division Workaround Does Not Work Partitioning the property to create a new flag lot does not avoid the Chapter 15.10 sewer connection requirement. The owners considered this path, reasoning that a new vacant parcel might qualify for different treatment under county wastewater rules and potentially allow a new septic system to serve a new structure. City of Bend Engineering confirmed in writing that this approach does not work. Partitioning triggers the sewer connection requirement before any vacant-lot exemptions apply. The land division creates a new parcel that is still inside city limits, still subject to Chapter 15.10, and still requires connection before construction begins. The workaround isn’t a workaround. The Sewer Was the Problem Here. Somewhere Else, It Will Be Something Different. Oregon’s ADU reform efforts have pushed toward making accessory dwelling units easier to build across urban areas. The intent is real.







