Retrofit Requirements:


On April 22, 2008, the Board of Supervisors approved two plumbing retrofit ordinances for the Los Osos and Nipomo Mesa areas. The ordinances address groundwater basin resource constraints by requiring both new and existing development to retrofit older, non-conserving toilets and shower heads with those that are water efficient.  The ordinances went effective May 22, 2008.

The Retrofit-On-Sale Program (Title 8) requires retrofit verification for all homes before sale. The Retrofit to-Build Program (Title 19) requires all new development that uses water from the Los Osos Groundwater Basin to retrofit older plumbing fixtures in existing homes and businesses to save twice the amount of water the new development will use.  

The retrofit requirements apply to properties inside and outside of the Sewer Service Area/Prohibition Zone (see map below).

Los Osos Sewer Service Area/Prohibition Zone Map:


To find out if your property is within the Sewer Service Area/Prohibition Zone, visit Land Use View.

  1. Enter the property address at the top right corner in the search engine and click "Enter". 

  2. On the left side panel, click the "+" icon next to "Planning", "Districts and Boundaries", and "RWQCB Prohibition Zones".

  3. Under the "District and Boundaries" header, check the box next to "Los Osos Prohibition Zone".

  4. If your property is located within the red lined boundary, it is in the Prohibition Zone/Sewer Service Area. 

  5. If you’re having trouble, please feel free to contact the Department of Planning and Building



Waitlist for Building Permits in the Sewer Service Area/Prohibition Zone (except ADUs):

The annual growth rate for new dwelling units (excluding affordable housing projects and Accessory Dwelling Units (ADUs)) in the Los Osos Prohibition Zone is currently 0%. When building permits are issued, 65% of the allowable dwelling units are reserved for single family dwellings and 35% for multi-family dwellings. These standards are outlined in the County's Growth Management Ordinance.


Properties outside of the Sewer Service Area/Prohibition Zone may apply for building permits at this time, subject to other County policies.

Click here for a FAQ about Vacant Lots in Los Osos.

Click here for the Single Family Dwelling Waitlist

to apply for single family dwelling building permits within the Prohibition Zone

Click here for the Multi-Family Waitlist

to apply for multi-family dwelling building permits within the Prohibition Zone

Click here for the application to be added to the waitlist.